Patent Publication Number: US-8994990-B2

Title: System management server, and management method and program

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to system management servers, and management methods and programs in a printing system in which print document information and printing device information of a tenant are assigned to a plurality of servers to perform distributed management. 
     2. Description of the Related Art 
     Conventionally, there is a known print document management system which manages document data to be printed and printers (print destinations). The print document management system receives document data from a user application or another document management system, produces print document information, and holds the print document information in association with the document data. Thereafter, the print document management system executes a printing process in response to a user&#39;s request for execution of printing, and adds the result of the printing process to the print document information. 
     In recent years, as the Internet has become widespread and the speed of networks has increased, functions conventionally provided by software have been more often provided as services on the Internet. The print document management system is also used as a back end for such services. Note that if a service is provided on the Internet, it is necessary to provide the service to a plurality of tenants (contracting entities (units), such as companies etc.). 
     In a data management method which is used when a service is provided to a plurality of tenants, a database is typically divided into areas for the respective tenants. Japanese Patent Laid-Open No. 2010-026653 proposes a data access control technique which can facilitate the development of an application which accesses a database having different data areas for respective tenants. 
     However, the print document management system serving as a back end for a service on the Internet needs to handle a much larger number of users, print documents, and printers than the number of those of an intranet. Therefore, the print document management system needs to be configured so that a plurality of servers can form a cluster. The print document management system also needs to be configured to handle an increased number of users, print documents, and printers by increasing the number of servers (scaling out). As a technique of achieving such a configuration, there is a distributed data technique called consistent hashing. 
     However, when a separate system (server) is assigned to each tenant, the operating ratio of a system (server) which provides a service to a small-scale tenant is low, leading to high operation cost of the entire service. On the other hand, when a single system provides a print service to a plurality of tenants, then if data is distributed without considering the tenants, the cost of a process which is performed on a tenant-by-tenant basis (e.g., scaling out) increases. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method and device which can easily perform a process on a tenant-by-tenant basis while reducing the operational cost of an entire service. 
     According to an embodiment of the present invention, there is provided a system management server for assigning print document information and printing device information of a tenant to a plurality of servers to perform distributed management in a printing system, the server comprising: a search unit configured to search the plurality of servers for a server for managing a given tenant when print document information and printing device information of the given tenant are divided and moved; a determination unit configured to determine the server found by the search unit to be a destination server of the movement when the server is allowed to store the divided print document information and printing device information; and a movement unit configured to move the divided print document information and printing device information to the destination server determined by the determination unit. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram showing an entire configuration of a print document management system. 
         FIG. 2  is a block diagram showing a hardware configuration of a client terminal and each server. 
         FIG. 3A  is a diagram showing a software configuration of an authentication server, and  FIG. 3B  is a diagram showing a software configuration of a printing system management server. 
         FIG. 4A  is a diagram showing a software configuration of a print request acceptance server, and  FIG. 4B  is a diagram showing a software configuration of a print document management server. 
         FIG. 5A  is a diagram showing a software configuration of a printing device management server, and  FIG. 5B  is a diagram showing a configuration of a print document data storage server. 
         FIG. 6A  is a diagram showing user information held by the authentication server, and  FIG. 6B  is a diagram showing print document assignment information and printing device assignment information held by the printing system management server. 
         FIG. 7  is a diagram showing print document information held by the print document management server. 
         FIG. 8  is a diagram showing printing device information held by the printing device management server. 
         FIG. 9A  is a diagram schematically showing the way in which distributed management is performed by a plurality of servers, and  FIG. 9B  is a diagram showing assignment information (database list). 
         FIG. 10  is a diagram schematically showing the way in which print document information or printing device information is managed in a distributed manner in a plurality of servers for each tenant. 
         FIG. 11  is a diagram schematically showing distributed management using assignment information (database list). 
         FIG. 12  is a diagram showing a process of printing performed in response to a print request from a client terminal. 
         FIG. 13  is a flowchart showing a process performed by the print request acceptance server. 
         FIG. 14  is a flowchart showing a process of the print document management server. 
         FIG. 15  is a flowchart showing a process of the printing device management server. 
         FIG. 16  is a flowchart showing a process of the printing device management server which has detected completion of printing of a printer. 
         FIG. 17  is a flowchart showing a process of the print document management server which has received a print completion notification from the printing device management server. 
         FIG. 18  is a diagram showing a user interface for instructing to perform scaling out. 
         FIG. 19  is a flowchart showing a process of the printing system management server which has received a scale-out request. 
         FIG. 20  is a flowchart showing a process of the printing system management server which has received a scale-out request. 
         FIG. 21  is a flowchart showing a process of the printing system management server which has received a scale-out request. 
         FIG. 22A  is a diagram schematically showing a process of dividing a database when scaling out is performed for a tenant, and  FIG. 22B  is a diagram schematically showing a process of moving a database obtained by division when scaling out is performed for a tenant. 
         FIG. 23  is a diagram schematically showing a process of moving a database obtained by division as shown in  FIG. 22B , using the assignment information (database list) of  FIG. 6B . 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Embodiments of the present invention will be described in detail hereinafter with reference to the attached drawings. Firstly, a print document management system in which an embodiment of the present invention will be carried out will be described with reference to  FIG. 1  which is a diagram showing an entire configuration of the print document management system. 
     As shown in  FIG. 1 , the print document management system includes a plurality of client terminals  101 , a plurality of printers  102 , an authentication server  103 , and a printing system management server  104 . The print document management system also includes a print request acceptance server  105 , a plurality of print document management servers  106 , a plurality of printing device management servers  107 , and a print document data storage server  108 . 
     Note that the terminals, the printers, and the servers included in the print document management system are connected together via a communication line (not shown). The communication line may be a so-called communication network which is implemented using one or a combination of a LAN and a WAN (e.g., the Internet, an intranet, etc.), a telephone line, a dedicated digital line, an ATM or frame relay line, a cable television line, a data broadcast wireless line, etc. The communication line may be any line that can be used to transmit and receive data, and different communication protocols may be used between the client terminals  101 , the printers  102 , and the servers. 
     The client terminal  101  may be, for example, a desk-top personal computer, a notebook personal computer, a mobile personal computer, a personal data assistant (PDA), etc., or may be a mobile telephone including an environment in which a program can be executed. The printer  102  may be a printer (e.g., a laser beam printer etc.) which can be connected to a network. 
     The authentication server  103  supports a protocol such as LDAP etc., provides a directory service, and manages user information in this system. The authentication server  103  performs user authentication in response to a request from the client terminal  101 . 
     The printing system management server  104  manages this entire system. The printing system management server manages assignment information of the print document management servers  106  and print document information, and assignment information of the printing device management servers  107  and printing devices. The print request acceptance server  105  receives a print request from the client terminal  101  and returns a response. 
     The print document management server  106  manages a state of print document data stored in the print document data storage server  108 . In response to a print request, the printing device management server  107  reads print document data stored in the print document data storage server  108 , converts the print document data into a format which can be interpreted by the printer  102 , and transmits the resulting print document data to the printer. The printing device management server also monitors and tracks a print job of the printer  102  until printing is completed. 
     The print document data storage server  108  holds print document data in association with print document information in a storage which can be connected directly to a network, such as a file server which supports a file sharing protocol such as SMB etc., a SAN, a NAS, etc. Here, SAN is an abbreviation for storage area network, and NAS is an abbreviation for network attached storage. 
     Next, a configuration of the client terminal  101 , the authentication server  103 , the printing system management server  104 , the print request acceptance server  105 , the print document management server  106 , the printing device management server  107 , and the print document data storage server  108  will be described with reference to  FIG. 2 .  FIG. 2  is a block diagram showing a basic hardware configuration of these devices. 
     In  FIG. 2 , a CPU  21 , a RAM  22 , a LAN adaptor  24 , a video adaptor  25 , an input unit (keyboard)  26 , an input unit (mouse)  27 , a hard disk  28 , and a CD-ROM drive  29  are connected together via a system bus  20 . The system bus  20  may include, for example, a PCI bus, an AGP bus, a memory bus, etc. Note that, in  FIG. 2 , a chip for connection between each bus, a keyboard interface, and an input/output interface (e.g., so-called SCSI or ATAPI, etc.) are not shown. 
     The CPU  21  performs various operations, such as four arithmetic operations, comparison operations, etc., and controls hardware, based on a program of an operating system or an application program. The RAM  22  is used to store a program of an operating system or an application program which is read from the hard disk  28  or a storage medium (e.g., a CD-ROM, a CD-R, etc.) loaded in the CD-ROM drive  29 . These programs are executed by the CPU  21 . 
     The ROM  23  stores, for example, a so-called BIOS, which controls input/output of data to/from the hard disk  28  etc. in cooperation with an operating system. The LAN adaptor  24  controls communication with an external device connected thereto via a network, in cooperation with a communication program of an operating system controlled by the CPU  21 . The video adaptor  25  generates an image signal which is to be output to a display device. The keyboard  26  and the mouse  27  are used to input an instruction to the client terminal  101 . 
     The hard disk  28  stores an operating system and an application program (e.g., a print document management system program etc.). The CD-ROM drive  29  is used to install into the hard disk  28  an application program read from a storage medium such as a CD-ROM, a CD-R, a CD-R/W, etc. which is loaded therein. Note that a CD-R drive, a CD-R/W drive, a DVD drive, etc. may of course be used. 
       FIGS. 3A to 5B  are diagrams showing software configurations of the servers included in this system. Note that  FIG. 3A  is a diagram showing a software configuration of the authentication server  103 . The authentication server  103  holds user information  302 . The authentication server includes an authentication unit  301  which accepts an authentication request from the client terminal  101 , and performs authentication based on the user information  302 . 
       FIG. 3B  is a diagram showing a software configuration of the printing system management server  104 . The printing system management server  104  holds print document assignment information  315  indicating assignment of the print document management servers  106  and print document information, and printing device assignment information  316  indicating assignment of the printing device management servers  107  and printing devices. The printing system management server includes an assignment information management unit  311  which manages the print document assignment information  315  and the printing device assignment information  316 . The printing system management server also includes a scale-out request acceptance unit  317  which accepts a scale-out request on a tenant-by-tenant basis when scaling out is performed for a tenant (division and movement of a database). The printing system management server also includes a movement database determination unit  312  which determines a database which is to be moved when scaling out is executed, a database movement destination determination unit  313  which determines a server which is a destination of the database to be moved, and a database movement execution unit  314  which executes movement of the database. 
       FIG. 4A  is a diagram showing a software configuration of the print request acceptance server  105 . The print request acceptance server  105  holds print document assignment information (cache)  406  which is obtained from the printing system management server  104 . The print request acceptance server includes an assignment information obtaining unit  401  which obtains print document assignment information from the printing system management server  104 . The print request acceptance server also includes a print request acceptance unit  402  which accepts a print request from the client terminal  101 , and a tenant identifier obtaining unit  403  which obtains a tenant identifier from the authentication server  103 . The print request acceptance server also includes a print document management server designation unit  404  which designates a print document management server  106  based on the print document assignment information (cache)  406 , and a print request transmission unit  405  which transmits a print request to the print document management server  106 . 
       FIG. 4B  is a diagram showing a software configuration of the print document management server  106 . The print document management server  106  holds print document information  417  which is used to manage a state of print document data stored in the print document data storage server  108 . The print document management server also holds printing device assignment information (cache)  418  and print document assignment information (cache)  419  which are obtained from the printing system management server  104 . The print document management server includes a print document management unit  411  which manages the print document information  417 . The print document management server also includes an assignment information obtaining unit  412  which obtains printing device assignment information from the printing system management server  104 . The print document management server also includes a print request reception unit  413  which receives a print request from the print request acceptance server  105 . The print document management server also includes a printing device management server designation unit  414  which designates a printing device management server  107  based on the printing device assignment information (cache)  418 , and a print request transmission unit  415  which transmits a print request to the printing device management server  107 . The print document management server also includes a print completion notification reception unit  420  which receives a print completion notification from the printing device management server  107 . The print document management server also includes a database division unit  416  which divides a database in accordance with an instruction from the printing system management server  104 . 
       FIG. 5A  is a diagram showing a software configuration of the printing device management server  107 . The printing device management server  107  holds printing device information  508  which is used to manage the printer  102 . The printing device management server also holds print document assignment information (cache)  509  and printing device assignment information (cache)  510  which are obtained from the printing system management server  104 . The printing device management server includes a printing device management unit  501  which manages the printing device information  508 . The printing device management server also includes an assignment information obtaining unit  502  which obtains print document assignment information from the printing system management server  104 . The printing device management server also includes a print request reception unit  503  which receives a print request from the print document management server  106 . The printing device management server also includes a print document management server designation unit  504  which designates a print document management server  106  based on the print document assignment information (cache)  509 , and a print result notification unit  506  which notifies the print document management server  106  of the print result. The printing device management server also includes a database division unit  507  which divides a database in accordance with an instruction from the printing system management server  104 .  FIG. 5B  is a diagram showing a configuration of the print document data storage server  108 . The print document data storage server  108  holds print document data  511 . 
     The information items held by the servers included in this system will now be described with reference to  FIGS. 6A to 8 .  FIG. 6A  is a diagram showing the user information  302  held by the authentication server  103 . The user information  302  contains a user list  601 . The user list  601  contains a list of individual-user information  602  containing a user ID, password, and tenant ID of each user. 
       FIG. 6B  is a diagram showing the print document assignment information  315  and the printing device assignment information  316  held by the printing system management server  104 . The print document assignment information  315  and the printing device assignment information  316  have the same structure and are collectively referred to as assignment information. Also shown are the print document assignment information (cache)  406  held by the print request acceptance server  105 , the printing device assignment information (cache)  418  held by the print document management server  106 , and the print document assignment information (cache)  509  held by the printing device management server  107 . 
     Here, the assignment information contains a tenant list  611 . The tenant list  611  contains a list of individual-tenant information  612  containing a tenant ID and database list of each tenant. The database list contains a list of individual-database information  613  containing a database name, integer value, server IP address, and update disable flag of each database. 
       FIG. 7  is a diagram showing the print document information  417  held by the print document management server  106 . The print document information  417  contains a tenant list  701 . The tenant list  701  contains a list of individual-tenant information  702  containing a tenant ID and database list of each tenant. The database list contains a list of individual-database information  703  containing a database name and owner list of each database. The owner list contains a list of individual-owner information  704  containing an owner ID and a print document list. The print document list contains a list of individual-print document information  705  containing a print document ID, a document name, the date and time of acceptance, the number of pages, the number of times of printing, and a status. 
       FIG. 8  is a diagram showing the printing device information  508  held by the printing device management server  107 . The printing device information  508  contains a tenant list  801 . The tenant list  801  contains a list of individual-tenant information  802  containing a tenant ID and database list of each tenant. The database list contains a list of individual-database information  803  containing a database name and printer list of each database. The printer list contains a list of individual-printing device information  804  containing a printer name, a model name, an IP address, a status, and a print job list. 
     Next, the way in which print document information or printing device information is managed in a distributed manner in this system will be described with reference to  FIGS. 9A to 11 .  FIG. 9A  is a diagram schematically showing the way in which print document information or printing device information is managed in a distributed manner using a plurality of servers. This diagram shows a ring  901  on which a value next to a maximum value is zero, in an integer value space. This diagram also shows databases  902  to  907  associated with respective integer values on the ring  901 . An integer value on the ring  901  is assigned to the first database encountered as one progresses clockwise on the ring. Here, an integer value  908  on the ring  901  is assigned to a database  903  which is the first database encountered as one progresses clockwise on the ring. 
     In this system, for print document information, a database is determined to which a hash value calculated from the ID of the owner of a print document is assigned as an integer value on the ring  901 . For printing device information, a database is determined to which a hash value calculated from the printer name of a printing device is assigned as an integer value on the ring  901 . 
       FIG. 9B  is a diagram schematically showing the distributed management of  FIG. 9A  using the assignment information (database list) of  FIG. 6B . A database has, as its attributes, a database name for identifying the database and an integer value on the ring  901  of  FIG. 9A . For example, if a hash value calculated from the ID of the owner of a print document is between the integer value 0 of a database “A- 1 ” and the integer value 357913941 of a database “A- 2 ,” the print document information is stored in the database “A- 2 .” If the hash value is between the integer value of the database “A- 2 ” and the integer value of a database “A- 3 ,” the print document information is stored in the database “A- 3 .” If the hash value is greater than the integer value 1789569705 of a database “A- 6 ,” the print document information is stored in the database “A- 1 .” A database also has, as its attribute, the IP address of a server to which the database is assigned. 
     In this system, a server holds at least one database. Print document information is stored in a database held by the print document management server  106 , and printing device information is stored in a database held by the printing device management server  107 . 
       FIG. 10  is a diagram schematically showing the way in which print document information or printing device information is managed in a distributed manner in a plurality of servers for each tenant. This diagram shows that the ring  901  of  FIG. 9A  is provided for each of tenants, an A-company  1001 , a B-company  1002 , and a C-company  1003 . This diagram also shows databases  1004  to  1006 ,  1007  and  1008 , and  1009  associated with integer values on the rings of the respective tenants. The number of databases for each tenant varies depending on the scale of the tenant. The number of databases increases with increasing tenant scale. This diagram also shows servers  1011  to  1013  holding the databases. In this example, the databases for the three tenants are distributed and managed in the three print document management servers. As shown in this example, databases for a tenant are not necessarily held by a single server (the databases for the A-company are held by a server  1  and a server  3 ). A server does not necessarily hold databases only for a single tenant (the server  3  holds databases of the A-company and the C-company). 
       FIG. 11  is a diagram schematically showing the distributed management of  FIG. 10  using the assignment information (database list) of  FIG. 6B . This diagram shows assignment information (database lists)  1101 ,  1102 , and  1103  of the A-company, the B-company, and the C-company respectively. 
     Next, in the print document management system, a flow of a printing process which is performed in response to a print request from the client terminal  101  will be described with reference to  FIG. 12 . Initially, the client terminal  101  accepts a user ID and a password input by a user, and transmits a user authentication request to the authentication server  103  ( 1201 ). If user authentication is successful, the authentication server  103  returns a session ID to the client terminal  101 . The client terminal  101  transmits the session ID received from the authentication server  103  and a print request to the print request acceptance server  105  in accordance with an instruction from the user ( 1202 ). Here, the print request contains an ID for identifying a print document, an ID for identifying the owner of the print document, and the name of a printer (print destination). 
     On the other hand, the print request acceptance server  105  which has accepted the print request transmits the session ID to the authentication server  103  ( 1203 ) to obtain a tenant ID belonging to the user who has requested printing. The print request acceptance server  105  designates a print document management server  106  based on the print document assignment information  419  using the tenant ID obtained from the authentication server  103  and the owner ID of a print document contained in the print request. The print request acceptance server transmits the tenant ID and the print request to the designated print document management server  106  ( 1204 ). After receiving the print request, the print document management server  106  transmits the tenant ID and the print request to a printing device management server  107  which is designated based on the printing device assignment information  418  using the tenant ID and the printer name contained in the print request ( 1205 ). 
     Here, if the transmission of the print request is successful, the print document management server  106  changes the state of the print document to “currently being printed.” The printing device management server  107  which has received the print request obtains print document data associated with a print document ID contained in the print request, from the print document data storage server  108  ( 1206 ). Thereafter, the printing device management server converts the print document data into a format which can be interpreted by the printer  102 , and transmits the resulting data to the printer  102  ( 1207 ). 
     When printing is completed in the printer  102 , the printing device management server  107  transmits the tenant ID and a print completion notification to a print document management server  106  which is designated based on the print document assignment information  419  using the owner ID of the print document contained in the print request ( 1208 ). Here, the print completion notification contains the print document ID, the owner ID of the print document, and the print result. After receiving the print completion notification, the print document management server  106  changes the state of the print document to “already printed,” and increments the number of times of printing by one. 
     Flows ( FIG. 12 ) of processes performed by the print request acceptance server  105 , the print document management server  106 , and the printing device management server  107  will now be described with reference to  FIGS. 13 to 17 .  FIG. 13  is a flowchart showing the flow of the process performed by the print request acceptance server  105 . The print request acceptance server  105  receives a session ID and a print request from the client terminal  101  in S 1301 , and transmits the session ID to the authentication server  103  to obtain a tenant ID in S 1302 . In S 1303 , the print request acceptance server  105  determines whether or not the obtained tenant ID is contained in the tenant list  611  of the print document assignment information (cache)  406  held in the print request acceptance server. If the determination result is positive, the process proceeds to S 1305 , and, otherwise, the process proceeds to S 1304 , in which the print document assignment information of a tenant identified by the tenant ID is obtained from the printing system management server  104 . 
     In S 1305 , the print request acceptance server identifies individual-tenant information  612  using the tenant ID, and individual-database information  613  about a database storing print document information using a hash value calculated from the owner ID of the print document contained in the print request. Next, in S 1306 , the print request acceptance server transmits the print request and the tenant ID to a print document management server  106  having a server IP address contained in the individual-database information  613  identified in S 1305 . The print request acceptance server receives a response from the print document management server  106  in S 1307 , and determines whether or not the response is an assignment information error in S 1308 . Here, if it is determined that the response is an assignment information error, there is a possibility that the print document assignment information  315  held by the printing system management server  104  has been updated. Therefore, the process returns to S 1304 , in which the print request acceptance server obtains the print document assignment information of a tenant identified by the tenant ID from the printing system management server  104 . On the other hand, if it is determined that the response from the print document management server  106  is not an assignment information error, the process proceeds to S 1309 , in which the print request acceptance server returns a response to the client terminal  101 . 
     Note that steps S 1301  and S 1309  are executed by the print request acceptance unit  402  of the print request acceptance server  105 . Step S 1302  is executed by the tenant identifier obtaining unit  403 . Steps S 1303  and  1304  are executed by the assignment information obtaining unit  401 . Step S 1305  is executed by the print document management server designation unit  404 . Steps S 1307  and  1308  are executed by the print request transmission unit  405 . 
       FIG. 14  is a flowchart showing the flow of the process performed by the print document management server  106 . In S 1401 , the print document management server  106  receives a tenant ID and a print request from the print request acceptance server  105 . In S 1402 , the print document management server  106  identifies individual-tenant information  612  using the tenant ID by referencing the print document assignment information (cache)  419  held by the print document management server. Specifically, the print document management server identifies individual-database information  613  about a database storing print document information, using a hash value calculated from the owner ID of a print document contained in the print request. Next, in S 1403 , the print document management server  106  determines whether or not the database identified in S 1402  is contained in the print document information  417  held by the print document management server. If the determination result is negative, the process proceeds to S 1411 , in which the print document management server returns an assignment information error as a response to the print request acceptance server  105 . If the determination result of S 1403  is positive, the process proceeds to S 1404 , in which the print document management server determines whether or not the update disable flag in the individual-database information  613  is set. If the determination result is positive, it is during scaling out, and therefore, the process proceeds to S 1412 , in which the print document management server returns an update disable error as a response to the print request acceptance server  105 . 
     On the other hand, if the determination result of S 1404  is negative, the process proceeds to S 1405 . In S 1405 , the print document management server  106  determines whether or not the tenant ID received from the print request acceptance server  105  is contained in the tenant list  611  of the printing device assignment information (cache)  418  held by the print document management server. If the determination result is positive, the process proceeds to S 1407 , and, otherwise, the process proceeds to S 1406 , in which the print document management server obtains the printing device assignment information of a tenant identified by the tenant ID from the printing system management server  104 . 
     In S 1407 , the print document management server identifies individual-tenant information  612  using the tenant ID, and individual-database information  613  about a database storing printing device information using a hash value calculated from a printer name contained in the print request. In S 1408 , the print document management server transmits the print request and the tenant ID to the printing device management server  107  having a server IP address contained in the individual-database information  613  identified in S 1407 . The print document management server receives a response from the printing device management server  107  in S 1409 , and determines whether or not the response is an assignment information error in S 1410 . Here, if it is determined that the response is an assignment information error, there is a possibility that the print document assignment information  315  held by the printing system management server  104  has been updated. Therefore, the process returns to S 1406 , in which the print document management server obtains the print document assignment information of a tenant identified by the tenant ID from the printing system management server  104 . On the other hand, if it is determined that the response from the printing device management server  107  is not an assignment information error, the process proceeds to S 1413 , in which the print document management server changes the status of individual-print document information  705  identified by a print document ID contained in the print request to “currently being printed.” In S 1414 , the print document management server returns a response to the print request acceptance server  105 . 
     Note that steps S 1401  to S 1404 , S 1411 , S 1412 , and S 1414  are executed by the print request reception unit  413  of the print document management server  106 . Steps S 1405  and S 1406  are executed by the assignment information obtaining unit  412 . Step S 1407  is executed by the printing device management server designation unit  414 . Steps S 1408  to S 1410  are executed by the print request transmission unit  415 . Step S 1413  is executed by the print document management unit  411 . 
     In the process flow of  FIG. 14 , in S 1406 , the print document management server obtains the printing device assignment information of a tenant identified by a tenant ID received from the print request acceptance server  105 . However, the print document management server may obtain printing device assignment information from the printing system management server  104  at a time different from that when a print request is accepted. In this case, the assignment information obtaining unit  412  obtains the printing device assignment information of a tenant identified by the tenant ID of print document information managed by the print document management unit  411 . 
       FIG. 15  is a flowchart showing the flow of the process performed by the printing device management server  107 . In S 1501 , the printing device management server  107  receives a tenant ID and a print request from the print document management server  106 . In S 1502 , the printing device management server  107  identifies individual-tenant information  612  using the tenant ID by referencing the printing device assignment information (cache)  510  held by the printing device management server. The printing device management server identifies individual-database information  613  about a database storing printing device information using a hash value calculated from a printer name contained in the print request. In S 1503 , the printing device management server  107  determines whether or not the database identified in S 1502  is contained in the printing device information  508  held by the printing device management server. If it is determined that the database is not contained, the process proceeds to S 1508 , in which the printing device management server returns an assignment information error as a response to the print document management server  106 . 
     On the other hand, if it is determined in S 1503  that the database identified in S 1502  is contained, the process proceeds to S 1504 . In S 1504 , the printing device management server determines whether or not the update disable flag of the individual-database information  613  is set. Here, if the determination result is positive, it is during scaling out, and therefore, the process proceeds to S 1507 , in which the printing device management server returns an update disable error as a response to the print document management server  106 . If the determination result is negative, the process proceeds to S 1505 , in which the printing device management server produces a print job. In the print job, the tenant ID, the owner ID of the print document, and the print document ID which are contained in the print request are saved. Thereafter, in S 1506 , the printing device management server returns a response to the print document management server  106 . 
     Note that steps S 1501  to S 1504 , S 1506 , S 1507 , and S 1508  are executed by the print request reception unit  503  of the printing device management server  107 . Step S 1505  is executed by a printing process unit. 
       FIG. 16  is a flowchart showing the flow of the process performed by the printing device management server  107  which has detected completion of printing of the printer  102 . In S 1601 , the printing device management server  107  determines whether or not the tenant ID of a print job is contained in the tenant list  611  of the print document assignment information (cache)  509  held by the printing device management server. Here, if the determination result is positive, the process proceeds to S 1603 , and, otherwise, the process proceeds to S 1602 . In S 1602 , the printing device management server obtains the print document assignment information of a tenant identified by the tenant ID from the printing system management server  104 . 
     In S 1603 , the printing device management server identifies individual-tenant information  612  using the tenant ID, and individual-database information  613  about a database storing print document information using a hash value calculated from the owner ID of a print document contained in the print job. In S 1604 , the printing device management server transmits a print completion notification and the tenant ID to the print document management server  106  having a server IP address contained in the individual-database information  613  identified in S 1603 . Thereafter, the printing device management server receives a response from the print document management server  106  in S 1605 , and determines whether or not the response is an assignment information error in S 1606 . Here, if it is determined that the response is an assignment information error, there is a possibility that the print document assignment information  315  held by the printing system management server  104  has been updated. Therefore, the process returns to S 1602 , in which the printing device management server obtains the print document assignment information of a tenant identified by the tenant ID from the printing system management server  104 . 
     On the other hand, if it is determined in S 1606  that the response from the print document management server  106  is not an assignment information error, the process proceeds to S 1607 , in which the printing device management server determines whether or not the response is an update disable error. Here, if the determination result is positive, the process proceeds to S 1604 , in which the printing device management server transmits a print completion notification and the tenant ID again. If the determination result of S 1607  is negative, the process proceeds to S 1608 , in which the printing device management server removes the print job. 
     Note that steps S 1601  and S 1602  are executed by the assignment information obtaining unit  502  of the printing device management server  107 . Step S 1603  is executed by the print document management server designation unit  504 . Steps S 1604  to S 1607  are executed by the print result notification unit  506 . Step S 1608  is executed by the printing process unit  505 . 
     In the process flow of  FIG. 16 , in S 1602 , the printing device management server obtains the print document assignment information of a tenant identified by the tenant ID of the print job. However, the printing device management server may obtain print document assignment information from the printing system management server  104  at a time different from that when the printing device management server detects completion of printing. In this case, the assignment information obtaining unit  502  obtains the printing device assignment information of a tenant identified by the tenant ID of printing device information managed by the printing device management unit  501 . 
       FIG. 17  is a flowchart showing the flow of the process performed by the print document management server  106  which has received a print completion notification from the printing device management server  107 . In S 1701 , the print document management server  106  receives a tenant ID and a print completion notification from the printing device management server  107 . In S 1702 , the print document management server  106  identifies individual-tenant information  612  using the tenant ID by referencing the print document assignment information (cache)  419  held by the print document management server. Specifically, the print document management server identifies individual-database information  613  about a database storing print document information using a hash value calculated from the owner ID of a print document contained in the print completion notification. 
     In S 1703 , the print document management server  106  determines whether or not the database identified in S 1702  is contained in the print document information  417  held by the print document management server. Here, if it is determined that the database is not contained, the process proceeds to S 1708 , in which the print document management server returns an assignment information error as a response to the printing device management server  107 . However, if it is determined that the database identified in S 1702  is contained, the process proceeds to S 1704 , in which the print document management server determines whether or not the update disable flag of the individual-database information  613  is set. Here, if the determination result is positive, it is during scaling out, and therefore, the process proceeds to S 1707 , in which the print document management server returns an update disable error as a response to the printing device management server  107 . If the determination result is negative, the process proceeds to S 1705 , in which the print document management server changes the status of individual-print document information  705  identified by a print document ID contained in the print completion notification to “already printed.” Thereafter, in S 1706 , the print document management server returns a response to the printing device management server  107 . 
     Note that steps S 1701  to S 1704 , S 1706 , S 1707 , and S 1708  are executed by the print completion notification reception unit  420  of the printing device management server  107 . Step S 1705  is executed by the print document management unit  411 . 
     Next, a process in which scaling out is performed while a tenant is designated in the print document management system will be described with reference to  FIGS. 18 to 23 . When an instruction to perform scaling out is given to the printing system management server  104 , the printing system management server  104  moves databases held by the print document management server  106  and the printing device management server  107 . When a database is moved, it is necessary to temporarily disable the database to be updated while a service for tenants other than a tenant for which scaling out is performed is not stopped. Therefore, only a database for a tenant for which scaling out is performed is moved. Note that if a database of a tenant is distributed in a large number of servers, the cost of a process performed on a tenant-by-tenant basis is high. Therefore, the number of servers which manage the same tenant, even after scaling out, needs to be minimized. 
       FIG. 18  is a diagram showing a user interface for instructing the printing system management server  104  to perform scaling out. A user interface screen  1801  includes a list box  1802  which is used to select a tenant for which scaling out is to be executed, and edit boxes  1803  and  1804  which are used to input the number of users and the number of printers which are expected after scaling out. Based on values input to the edit boxes  1803  and  1804 , the printing system management server  104  determines the number of databases of print document information and printing device information, and divides and moves existing databases. The user interface screen  1801  also includes a cancel button  1805  and an OK button  1806 , and, if the OK button  1806  is pressed, a scale-out request is transmitted to the printing system management server  104 . The scale-out request contains values which have been input on the user interface screen  1801  to instruct to perform scaling out. 
       FIGS. 19 to 21  are flowcharts showing a flow of a process performed by the printing system management server  104  which receives a scale-out request. In S 1901 , the printing system management server receives a scale-out request. The scale-out request contains values  1802  and  1803  indicating the number of users and the number of printers, respectively, specified on the user interface screen  1801 . In S 1902 , based on the values contained in the scale-out request, the printing system management server determines the number of portions into which databases of print document information and printing device information are to be divided, and databases to be divided. Here, as the number of users increases, the number of portions into which a database of print document information is to be divided is increased. Also, as the number of printers increases, the number of portions into which a database of print device information is to be divided is increased. 
     Next, in S 1903 , the printing system management server searches for a server which holds a database or databases the number of which exceeds an upper limit due to the database division. In S 1904 , if the printing system management server determines that a server for which the upper limit is exceeded has been found, the process proceeds to S 1905 , in which the printing system management server determines whether or not the server for which the upper limit is exceeded also has a database for a tenant other than the tenant for which scaling out is to be executed. If the determination result is negative, the process proceeds to S 1907 , in which the printing system management server adds all database(s) for the tenant for which scaling out is to be executed, to databases to be moved, and returns to S 1903 . 
     On the other hand, if the determination result is positive, the process proceeds to S 1906 , in which the printing system management server adds an extra database(s) beyond the upper limit of the number of databases held by a server, to databases to be moved, and the process returns to S 1903 . Thereafter, the above process is repeated until no server for which the upper limit is exceeded is found in S 1904 . 
     If no server for which the upper limit exceeded is found in S 1904 , the process proceeds to S 2001  ( FIG. 20 ), in which the printing system management server searches for a server which can store all databases to be moved (the upper limit of the number of databases is not exceeded). If such a server has been found in S 2002 , the process proceeds to S 2003 . Otherwise, the process proceeds to S 2005 , in which an additional server is activated, and then proceeds to S 2003 . 
     In S 2003 , the server found in S 2002  or the server activated in S 2005  is determined to be a destination of a database(s) until the number of databases in the server reaches the upper limit. In S 2004 , the printing system management server determines whether or not a destination has been determined for all databases to be moved, and, if the determination result is negative, the process returns to S 2001 . 
     On the other hand, if the determination result is positive, the process proceeds to S 2005 , in which the assignment information ( 315 ,  316 ) held in the printing system management server  104  is updated based on the database division. Next, in S 2101  ( FIG. 21 ), the printing system management server sets the update disable flags of all the individual-database information  613  contained in the assignment information of the tenant for which scaling out is to be executed. Thereafter, in S 2102 , the printing system management server transmits the assignment information and an assignment information update request to all print document management servers and printing device management servers holding the assignment information cache. 
     Next, in S 2103 , the printing system management server transmits a database divide request to the print document management server and the printing device management server which hold the databases to be divided in S 1902  of  FIG. 19 . The print document management server, when receiving the database divide request, executes database division using the database division unit  416 . The printing device management server, when receiving the database divide request, executes database division using the database division unit  507 . Thereafter, in S 2104 , the printing system management server moves the databases determined to be moved in S 1906  and S 1907  of  FIG. 19  to a server which has been determined to be a destination in S 2003  of  FIG. 20 . Next, in S 2105 , the printing system management server resets the update disable flags of all the individual-database information  613  contained in the assignment information of the tenant for which scaling out is to be executed so update is possible. Thereafter, in S 2102 , the printing system management server transmits the assignment information and an assignment information update request to all print document management servers and printing device management servers holding the assignment information cache. 
     Note that step S 1901  of  FIG. 19  is executed by the scale-out request acceptance unit  317  of the printing system management server  104 . Steps S 1902  to S 1905  and S 1907  are executed by the movement database determination unit  312 . Steps S 2001  to S 2004  and S 2005  of  FIG. 20  are executed by the database movement destination determination unit  313 . Step S 2005  is executed by the assignment information management unit  311 . Steps S 2101  to S 2106  of  FIG. 21  are executed by the database movement execution unit  314 . 
       FIG. 22A  is a diagram schematically showing a process of dividing a database when scaling out is performed for a tenant. Rings  2201  and  2202  of  FIG. 22A  correspond to the ring  901  of  FIG. 9A  before and after division. In this example, while only a database  2203  is provided before division, two databases  2204  and  2205  are provided after division. In this case, after division, a portion of data stored in the database  2203  is moved to the database  2205 , and the remainder of the data which has not been moved is stored in the database  2204 . 
       FIG. 22B  is a diagram schematically showing a process of moving a database obtained by division when scaling out is performed for a tenant. A server  2211  holds a database  2213  for an A-company and a database  2214  for a C-company. Thereafter, the database  2214  of the server  2211  is divided, so that the number of databases held in the server exceeds the upper limit, and therefore, the database is moved as databases  2215  and  2216  to an additional server  2212  which is newly activated. 
       FIG. 23  is a diagram schematically showing a process of moving a database obtained by division as shown in  FIG. 22B , using the assignment information (database list) of  FIG. 6B . In this example, assignment information (database list)  2301 ,  2302 , and  2303  of an A-company, a B-company, and a C-company are changed, after division, into assignment information (database list)  2304 ,  2305 , and  2306  of the A-company, the B-company, and the C-company. 
     According to the above embodiment, a data management method of a print document management service which can easily perform a process on a tenant-by-tenant basis while reducing the operation cost of the entire service, can be provided. 
     Since only a database(s) for a tenant for which scaling out is to be executed is moved, scaling out can be executed without stopping a service for a tenant other than a tenant for which scaling out is to be executed. 
     When a database is divided in a server which also has a database for another tenant, then if the number of databases held in the server exceeds the upper limit, all database(s) for a tenant for which scaling out is to be executed is moved to an additional server which is newly activated. As a result, the number of servers which manage the same tenant, even after scaling out, can be minimized. 
     Other Embodiments 
     Aspects of the present invention can also be realized by a computer of a system or apparatus (or devices such as a CPU or MPU) that reads out and executes a program recorded on a memory device to perform the functions of the above-described embodiment, and by a method, the steps of which are performed by a computer of a system or apparatus by, for example, reading out and executing a program recorded on a memory device to perform the functions of the above-described embodiment. For this purpose, the program is provided to the computer for example via a network or from a recording medium of various types serving as the memory device (e.g., computer-readable medium). 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2011-106626, filed May 11, 2011, which is hereby incorporated by reference herein in its entirety.