Patent Publication Number: US-2009237828-A1

Title: Tape device data transferring method and tape management system

Description:
INCORPORATION BY REFERENCE 
     The present application claims priority from Japanese application JP2008-072041 filed on Mar. 19, 2008, the content of which is hereby incorporated by reference into this application. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a technology for transferring data of a tape device capable of transferring data in a non-stop state. 
     2. Description of the Related Art 
     Computer systems generally use magnetic discs or magnetic tapes as media for data storage. Magnetic discs are used to record data that are frequently used because they are capable of a so-called random access that allows direct access to data recorded at arbitrary locations on the magnetic discs. Magnetic tapes on the other hand are storage media capable of only a so-called sequential access that allows sequential data read or write from the start of the tape, so they are mainly used for such applications as backup of data recorded on magnetic discs and long-term storage of old data. The main reason for using the magnetic tapes for backup and archiving is that a bit cost of the magnetic tapes is lower than that of the magnetic discs and costs less when storing a large volume of data. 
     However, in recent years, the magnetic tapes are being phased out of service because of its performance and storage capacity and some devices have already been removed from production line. Under these circumstances, as disclosed in JP-A-2005-99971, there is a trend to move systems from the conventional tape devices to virtual tape devices that use magnetic disks to emulate tape devices and to large-capacity, high-speed LTO (Linear Tape Open) devices. This requires transferring data from a source tape volume to a destination tape volume. 
     As to magnetic discs, JP-A-11-184641 discloses a technique to move data from magnetic discs to other magnetic discs uninterrupted during operation in order to avoid adverse effects on tasks being executed by a host. 
     Further, in magnetic tape devices, JP-A-2008-27335 discloses a data transferring technique that erases data in a source device after the data is moved to a destination device. With this method, the data transfer can be done without interrupting the business transactions. However, this method makes it necessary to build a storage system that, in addition to a first storage device or source device and a second storage device or destination device, has a new data transferring device for moving data from the first storage device to the second storage device. 
     SUMMARY OF THE INVENTION 
     While JP-A-2008-27335 provides a new data transferring device, it is not preferable to prepare a new device in moving data from one magnetic tape device to another because data transfer is only performed in limited cases where storage devices are introduced. Further, since the technique disclosed by JP-A-2008-27335 does not update file management information in connection with the data transfer, it is necessary to execute such operations as updating file location information in a destination volume after the data transfer is completed. 
     On the other hand, to execute a data transfer by the conventional method without introducing a new device, the transactions being executed by the host must be interrupted temporarily. Although the magnetic tape device is used mainly for backup, halting accesses, even temporarily, to the magnetic tape device means an interruption to the customer transactions and adverse effects caused by the data transfer operation are great. For customers who need 24-hour on-line transactions, in particular, this temporary service interruption is not tolerable. This raises a technical problem that a system transfer cannot be performed. 
     It is an object of the present invention to solve the above-mentioned problems and to provide a data transferring method for tape devices to transfer data with no service interruptions, i.e., without interrupting accesses by a higher-level devices to the tape devices during a data transfer procedure, and without introducing a new device. It is also an object of the invention to provide a tape management system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a configuration diagram of a tape management system in a first embodiment of the invention. 
         FIG. 2  is an explanatory diagram showing an example of a tape device conversion table. 
         FIG. 3  is an explanatory diagram showing an example of a journal. 
         FIG. 4  is an explanatory diagram showing a magnetic tape library management table and a virtual tape management table. 
         FIG. 5  is an explanatory diagram showing an example of content of a tape volume in a data transfer interrupted state. 
         FIG. 6  is a flow chart showing a data transfer operation in response to a data transfer request. 
         FIG. 7  is a flow chart showing a tape volume access operation in response to a tape volume access request that occurs while data is being transferred. 
         FIG. 8  is a configuration diagram of a tape management system in a second embodiment of the invention. 
         FIG. 9  is a flow chart showing a data transfer operation in response to a data transfer request in the second embodiment. 
         FIG. 10  is an explanatory diagram showing an example of a tape device conversion table in the second embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENT 
     Now, preferred embodiments of this invention (hereinafter referred to simply as embodiments) will be described. It should be noted that the invention is not limited in any way by the embodiments. 
     First Embodiment 
       FIG. 1  is a configuration diagram showing a tape management system in the first embodiment. In the system configuration of  FIG. 1 , a host computer  100  is connected with a magnetic tape library device  130 , a magnetic disc device  140  and an input/output terminal  160 . This embodiment of the invention requires a system configuration in which one or more host computers  100  are connected with one or more tape devices, such as magnetic tape library devices  130  and virtual tape devices (that are virtually built in a magnetic disc device  140 ) so that they can communicate with one another. The system configuration of this embodiment also requires that an input/output terminal  160  be connected to the host computer  100  to give the host computer instructions on a data transfer operation and a request for access to a tape volume. 
     The host computer  100  is a device to process information used by the user and has a CPU (Central Processing Unit)  110 , a memory (storage unit)  120  and a connecting unit for connecting these, such as buses and switches. The CPU  110  executes a variety of programs stored in the memory  120 . The memory  120  holds various programs to be executed by the host computer  100  and temporary data. The magnetic tape library device  130  and the magnetic disc device  140  store various data to be used by the host computer  100  in executing the programs. 
     The memory  120  has stored therein a tape volume use program  111 , a data transfer program  112 , an input/output control program  113  to control requests for access to various external storage devices, and a device allocation control program  117  to allocate a tape volume to a tape device to be used. 
     The memory  120  also has stored therein a magnetic tape library control program  118  and a virtual tape control program  116 . When a magnetic tape library device  130  is used as the tape device, the magnetic tape library control program  118  is executed to control the magnetic tape library device  130  to operate a magnetic tape library management table  150  (see  FIG. 4 ). When a virtual tape device is used as the tape device, the virtual tape control program  116  is executed to control the virtual tape device to operate a virtual tape management table  152  (see  FIG. 4 ). 
     The tape volume use program  111  is a user transaction program that uses tape volumes of tape devices connected to the host computer  100 . 
     The data transfer program  112  performs a variety of controls to move data among tape volumes of tape devices connected to the host computer  100 . It includes a data transfer control unit  114 , a management information control unit  115 , a tape device conversion table  121  (see  FIG. 2 ) and a journal  122  (see  FIG. 3 ). 
     The data transfer control unit  114  performs a data transfer operation among tape volumes. At this time, it records a state of data transfer (tape volume names, file ordinal numbers of files whose data is being moved, etc.) in the journal  122 . For example, when the user instructs an execution of data transfer from the input/output terminal  160 , the data transfer control unit  114  uses the specified source tape device ( 131  in this embodiment) to connect a tape volume ( 132  in this embodiment) and execute the input operation. It then moves the input data into a tape volume ( 142  in this embodiment) that is connected by using the specified destination tape device (virtual tape device in this embodiment). If, while data is being moved, a request for access to the tape volume of interest should occur, the data transfer control unit  114  interrupts the data transfer operation and gives priority to the access request. After the access request for the volume in question is completed, the data transfer control unit  114  resumes the data transfer operation. 
     If the data transfer control unit  114  receives a user instruction in advance, it generates a tape device conversion table  121  before starting the data transfer operation. Or the data transfer control unit  114  generates a tape device conversion table  121  during execution of the data transfer operation. 
     In the tape device conversion table  121  are stored names of tape volumes to be used for data transfer and names of source/destination tape devices. If a request for access to the tape volume of interest occurs during the data transfer operation, the tape device conversion table  121  is used to switch between the requests for access to the source and destination tape volumes. 
     The management information control unit  115 , when the data transfer operation is started, manipulates various management information, including the magnetic tape library management table  150  (see  FIG. 4 ), the virtual tape management table  152  (see  FIG. 4 ) and a file registration table  151 , to control the access request to the source or destination tape volume, thereby supporting the data transfer. An access request destination can be selected when the user makes a data transfer instruction, making it possible to prevent an access request from being made to fewer source or destination tape devices than is necessary. 
     For example, if the number of magnetic tape devices  131  is smaller than that of virtual tape devices, a magnetic tape library control program  118  changes the volume information managed by the magnetic tape library management table  150  into an unusable state in order to prevent an access request to the source magnetic tape volume  132  from being made. And a virtual tape control program  116  changes the volume information managed by the virtual tape management table  152  into a usable state in order to allow an access request to the destination virtual tape volume  142  to be accepted. As a result, the access requests to the tape volume from which data is being moved are all changed to access requests to the destination virtual tape volume  142 . An access request destination is then controlled by the input/output control program  113 , thus preventing a possible stoppage of transaction due to the data transfer. 
     Conversely, if the number of virtual tape devices is smaller than that of magnetic tape devices  131 , the virtual tape control program  116  changes the volume information managed by the virtual tape management table  152  into the unusable state in order to prevent an access request to the destination virtual tape volume  142  from being made. The volume information managed by the magnetic tape library management table  150  is changed by the magnetic tape library control program  118  into the usable state in order to allow an access request to the source magnetic tape volume  132  to be accepted. This causes the access requests to the tape volume into which data is being moved are changed to access requests to the source magnetic tape volume  132 . An access request destination is then controlled by the input/output control program  113 . 
     The management information control unit  115 , after the data transfer is completed, updates information in the file registration table  151  to access files in the destination tape volume, thus supporting the data transfer operation. 
     In the file registration table  151  there are stored information on names and locations of files paired with attributes of storage devices. Since the system automatically recognizes the locations of files according to the file registration table  151 , the user does not need to perform management on the file locations or specify job control statements. Therefore, after the data transfer is complete, it is necessary to correct the information on the transferred files by changing the source tape volume to the destination tape volume. These file information management is done by the management information control unit  115 . 
     The input/output control program  113  is part of the functions of general OS (Operating System) and executes an input/output operation on the devices connected to the host computer  100 . 
     The device allocation control program  117  is part of the functions of general OS and allocates a medium in which files are stored to devices, so that files specified during the input/output operation can be used. When the tape volume use program  111  is executed, the device allocation control program  117  selects a device and a tape volume to be processed by referring to information on the tape device conversion table  121  and the journal  122  and allocates a device before the input/output control program  113  performs the input/output operation. 
     For example, if a tape volume to be processed is connected to a source tape device registered with the tape device conversion table  121  (see  FIG. 2 ), the destination of connection is converted into the destination tape device and allocated before using the tape volume of interest. Further, from the information in the journal  122  (see  FIG. 3 ), the source/destination tape volumes are switched in executing the input/output processing. 
     The magnetic tape library control program  118  performs control on the magnetic tape library device  130  connected to the host computer  100 . The magnetic tape library device  130  is controlled by a magnetic tape library control device  133  to operate a built-in robot to automatically mount the magnetic tape volume  132 , for which an access request has occurred, on the specified magnetic tape device  131 . The magnetic tape volume  132  in the magnetic tape library device  130  is managed by the magnetic tape library management table  150  on a magnetic disc volume  141   b  ( 141 ) connected to the magnetic disc control device  143  in the magnetic disc device  140 . The magnetic tape library management table  150  stores medium information such as tape volume names. The magnetic tape library management table  150  is operated by the magnetic tape library control program  118 . 
     The virtual tape control program  116  performs control on the virtual tape devices virtually connected to the host computer  100  and, according to a demand from the input/output control program  113 , emulates the tape devices to control the input/output operation on the virtual tape volume  142  using the virtual tape devices. Actual data is stored on the magnetic disc volume  141   a  ( 141 ) connected to the magnetic disc control device  143  in the magnetic disc device  140 . The virtual tape volume  142  is managed by the virtual tape management table  152  on the magnetic disc volume  141   b . In the virtual tape management table  152  are stored medium information including virtual tape volume names. The virtual tape management table  152  is operated by the virtual tape control program  116 . 
     The input/output terminal  160  can be used to instruct the host computer  100  to process a data transfer to a tape device and an access request to a tape volume. 
     The magnetic tape library device  130  and the virtual tape device shown in the first embodiment of this invention represent one example configuration having a management table to manage tape volumes as tape devices. 
       FIG. 2  is an example of the tape device conversion table. The tape device conversion table  121  has registered therein information about tape volume names  200  of tape volumes to be data-transferred, source tape device names  201  and destination tape device names  202 . For example, registered information in a row  210  represents a case where a magnetic tape volume  132  with a tape volume name VOL 001 , which is used in a source tape device name TAPE 1  of the magnetic tape devices  131 , is transferred to a virtual tape volume  142  with a tape volume name VOL 001 , which is used in a virtual tape device name VTAPE 1 . 
       FIG. 3  shows one example of journal. The journal  122  records information about the processing state of data transfer (transfer state) in units of block. The information includes a tape volume name  300 , a source tape device name  301 , a status  302 , a transfer start time  303 , a last update time  304 , a file ordinal number  305  and a block number  306 . The journal  122  manages status  302 , such as “copying” if the data transfer is being executed and “copy interrupted” if the data transfer is interrupted. The file ordinal number  305  stores ordinal numbers of files for which the data transfer has been completed. Likewise, the block number  306  stores block numbers for which the data transfer has been finished. For example, a row  310  shows that a tape volume name VOL 001  of a source tape device name TAPE 1  is “being copied” and that the data transfer has been completed up to block number  14  of the file ordinal number  1 . 
       FIG. 4  is an explanatory diagram showing one example of a magnetic tape library management table and a virtual tape management table. The magnetic tape library management table  150  stores information used to manage the magnetic tape volumes  132  in the magnetic tape library devices  130 . More specifically, what is registered with the magnetic tape library management table  150  includes magnetic tape volume names  400  to be managed and statuses  401  indicating whether a particular magnetic tape volume  132  is usable or not usable. 
     Likewise, the virtual tape management table  152  stores information used to manage the virtual tape volumes  142  in the virtual tape devices. More specifically, the information registered includes virtual tape volume names  410  to be managed and statuses  411  indicating whether a particular virtual tape volume  142  is usable or not usable. 
       FIG. 5  is an explanatory diagram showing an example content of a tape volume whose data transfer operation is halted temporarily. If during data transfer operation an access request is made to a tape volume being processed, the data transfer is interrupted and an access request is given priority. So, the destination tape volume may become interrupted in units of block. For example, on a magnetic tape volume  132  of a tape volume name VOL 001  there are stored a plurality of files  501  (e.g., file  501   a  of file ordinal number  1  (file  1 ) and file  501   b  of file ordinal number  2  (file  2 ), with each file  501  made up of a plurality of blocks  502  (e.g., blocks  502   a ,  502   b ). In this case, if, while data of “file ordinal number  2 , block number  14 ” (as indicated by  310  of  FIG. 3 ) on the magnetic tape volume (VOL 001 )  132  is being transferred, an access request to the tape volume being processed occurs, the status  302  is changed from “being copied” to “copy interrupted” after the data transfer of the block being processed is finished, thus interrupting the data transfer operation. The status of the destination virtual tape volume  142  at this time is that files  511  have been stored up to block number  14  of block  512  of file ordinal number  2 . 
     The first embodiment has the following features. That is, when the input/output terminal  160  makes an access request to a tape volume being processed, (1) the data transfer that is being executed by the data transfer program  112  of the host computer  100  can be interrupted in units of block; and (2) the input/output control program  113  of the host computer  100  allows the input/output operation to be executed by changing the tape device and tape volume to be used according to the information on the tape device conversion table  121  and journal  122 . These features allow the data transfer to be performed without stopping transactions or without the user having to be aware of the destination/source tape volumes when accessing the tape volumes. 
     A process of transferring data from a magnetic tape volume  132  in the magnetic tape library device  130  to a virtual tape volume  142  in the virtual tape device will be explained as follows. 
       FIG. 6  is a flow chart showing how the data transfer operation is executed when a data transfer request is made. By referring to  FIG. 6  (also  FIG. 1  as required), the data transfer operation as performed by the CPU  110  will be explained. 
     When the input/output terminal  160  instructs the host computer  100  to execute a data transfer operation, the CPU  110  of the host computer  100  executes a variety of programs. Here these programs and devices are referred to as programs and processing units concerned. The data transfer program  112  starts the data transfer operation. There are two cases for the data transfer operation: one is when the data transfer operation is executed for the first time on the tape volume of interest; and another is when the data transfer operation is resumed from the middle of the tape volume whose data transfer operation has been suspended as by I/O (Input/Output) errors 
     First, the data transfer control unit  114  registers in the journal  122  information of the magnetic tape volume  132  to be processed (step S 600 ). If the data transfer is executed for the first time, information is newly registered as a “being copied” state. If the data transfer is executed on the magnetic tape volume  132  which is in a “copy interrupted” state, the existing information is updated to a “being copied” state. 
     Next, the management information control unit  115  updates the management information (management table) of tape volumes (step S 601 ). The magnetic tape library control program  118  updates the source magnetic tape library management table  150 , followed by the virtual tape control program  116  updating the destination virtual tape management table  152 . Here it is assumed that the user has selected a method whereby access requests to the tape volume currently being data-transferred are all changed to access requests to destination virtual tape volume  142  and that the user instructs the selected method at time of executing the data transfer operation. Thus, the source magnetic tape volume  132  managed by the source magnetic tape library management table  150  is updated to an unusable state. Further, the destination virtual tape volume  142  managed by the destination virtual tape management table  152  is updated to a usable state. If, when updating the management table, the tape volume of interest is already in the intended state, no updating is done on the management table. 
     Then, the data transfer control unit  114  checks if information on the magnetic tape volume  132  of interest is already registered (generated) in the tape device conversion table  121  (step S 602 ). If the information is not registered (No in step S 602 ), the data transfer control unit  114  newly registers information with the tape device conversion table  121  (step S 603 ). If it is registered (Yes in step S 602 ), the step S 603  is skipped. 
     Next, the data transfer control unit  114  executes a data copy operation. The data copy is performed one block at a time in order to be able to accept access requests from other devices (step S 604 ). The data transfer control unit  114  checks if there is any I/O error (step S 605 ). If the data copy has been performed with no I/O errors (No in step S 605 ), it updates the information in the journal  122  (step S 607 ). In the journal  122  the data transfer control unit  114  updates the copied block number and the last updated date and time one block at a time and also updates the copied file ordinal number one file at a time. The data transfer control unit  114  checks whether the end of data is reached (step S 608 ). If the end of data is not reached (No in step S 608 ), the data transfer control unit  114  checks if there is any access request from other devices (step S 612 ). If no access request occurs (No in step S 612 ), it returns to step S 604 . 
     If an I/O error has occurred during the data copy operation (Yes in step S 605 ), the data transfer control unit  114  updates the information of the journal  122  from the “being copied” state to the “copy interrupted” state (step S 606 ) before exiting the data transfer operation. 
     If during data copy operation the end of data is detected (Yes in step S 608 ), the data copy is ended. So, the management information control unit  115  updates the file registration table  151  that manages the file locations (step S 609 ) and the data transfer control unit  114  deletes the information (corresponding one record) of the journal  122  associated with the magnetic tape volume  132  of interest (step S 610 ) and also deletes the information (corresponding one record) of the tape device conversion table  121  associated with the tape volume of interest (step S 611 ). Updating the information in the file registration table  151  here involves correcting the information on the data-transferred file from the source magnetic tape volume  132  to the destination virtual tape volume  142 . 
     If during the data copy operation the data transfer control unit  114  detects an access request from other device (Yes in step S 612 ), as when an open request to the file being processed is issued from the input/output control program  113 , the data transfer control unit  114  gives priority to the access request by updating the information in the journal  122  about the magnetic tape volume  132  of interest from the “being copied” state to a “copy interrupted” state (step S 613 ). 
     Then the data transfer control unit  114  suspends the data copy operation for the input/output control program  113  to execute the tape volume access operation (see  FIG. 7 ) (step S 614 ). When the volume access operation is ended as by the input/output control program  113  issuing a close request to the file being processed, the data transfer control unit  114  updates the information of journal  122  about the magnetic tape volume  132  of interest from the “copy interrupted” state to the “being copied” state (step S 615 ) to resume the data copy operation (returning to step S 604 ). 
     The above sequence of steps allows the data transfer operation, that has a function of suspending the data transfer in the event that an access request is made from other device, to be executed by managing the data transfer state. 
       FIG. 7  is a flow chart showing how a tape volume is accessed when a tape volume access request is issued during a data transfer operation. The tape volume access operation as performed by the CPU  110  will be explained below by referring to  FIG. 7  (also  FIG. 1  as required). 
     When, in response to an instruction by the input/output terminal  160 , the host computer  100  executes the tape volume use program  111 , the input/output control program  113  executed by the CPU  110  of the host computer  100  starts the tape volume access operation. 
     First, the device allocation control program  117  allocates the access-requested tape volume to a tape device (step S 700 ). At this time, if information on the tape volume of interest is registered with the tape device conversion table  121 , the allocation device is changed from the source tape device to the de 
     Next, the input/output control program  113  checks whether the access request to the file to be processed is for an input system or output system (step S 701 ). If the access request is for the input system (Yes in step S 701 ), the input/output control program  113  then checks whether the request is for a file that has already been transferred (step S 702 ). In the following processing, the control program decides which of the source tape volume or the destination tape volume should be accessed, by using the file ordinal number of the file to be processed and the file ordinal number of the data-transferred file stored in the journal  122 . 
     If the access request is for the data-transferred file (Yes in step S 702 ), the device allocation control program  117  checks if the tape volume currently allocated is the destination tape volume, in order to access data stored in the destination tape volume. If the source tape volume is found allocated, the device allocation control program  117  changes the allocation to the destination tape volume according to a definition of the tape device conversion table  121  (step S 703 ). Then, the input/output control program  113  accesses data stored in the destination tape volume (step S 704 ) before proceeding to step S 711 . 
     If the access request is for a file whose data has not been moved (No in step S 702 ), the device allocation control program  117  checks if the currently allocated tape volume is the source tape volume. If the destination tape volume is found allocated, the device allocation control program  117  changes the allocation to the source tape volume according to information on tape volume of interest stored in the tape device conversion table  121  (step S 705 ). Then the input/output control program  113  accesses data stored in the source tape volume (step S 706 ) before moving to step S 711 . 
     Let us consider an example case in which the data transfer is suspended in a state shown in  FIG. 5 . If the request is for an input system having data of “file ordinal number  2 , block number  15 ” on the magnetic tape volume  132 , it is an access request to a file  501   b  which has yet to finish the data transfer. So, the input/output control program  113  accesses data stored in the magnetic tape volume  132 . If the request is for an input system having data of “file ordinal number  1 , block number  2 ”, it is an access request to a file  501   a  which has already finished the data transfer. So, the input/output control program  113  accesses data stored in the virtual tape volume  142 . 
     If the access request concerns an output system (No in step S 701 ), the input/output control program  113  clears (changes) the file ordinal number and block number of the data-transferred file in the tape volume information of the journal  122  (step S 707 ) to delete transferred data from the destination tape volume (step S 708 ). 
     Then, to access the source tape volume, the device allocation control program  117  checks if the currently allocated tape volume is the source tape volume. If the destination tape volume is found allocated, the device allocation control program  117  changes the allocation to the source tape volume according to the tape volume information in the tape device conversion table  121  (step S 709 ) so that the input/output control program  113  can access the source tape volume (step S 710 ). 
     The reason that the data in the destination tape volume is deleted in the event an output system access request is made is that the tape volume is sequentially accessed and, once an output is executed, the subsequent data needs to be treated as invalid and that when there are data in both the source and destination tape volumes, it cannot be determined to what extent the data is valid. Therefore, when an output system access request is made for the tape volume being data-transferred, the data transfer operation needs to be re-executed from the scratch. 
     Take for example a case where a data transfer operation is suspended in a state shown in  FIG. 5 . If an output system access request is made for data of “file ordinal number  2 , block number  151 ” in the magnetic tape volume  132 , the operation performed involves clearing the file ordinal number and block number in the information of the journal  122 , deleting the data of the virtual tape volume  142  that has already been data-transferred, and accessing the magnetic tape volume  132 . Similarly, if an output system access request is made for data of “file ordinal number  1 , block number  2 ” in the magnetic tape volume  132 , the operation performed involves clearing the file ordinal number and block number in the information of the journal  122 , deleting the data of the virtual tape volume  142  that has already been data-transferred, and accessing the magnetic tape volume  132 . 
     When the access request to the file of interest is completed, the device allocation control program  117  frees the tape device allocation (step S 711 ). With the above steps, an access request to the tape volume being data-transferred is executed. 
     Second Embodiment 
       FIG. 8  is a configuration diagram of a tape management system in a second embodiment. The difference in configuration between the second embodiment and  FIG. 1  is that the tape device connected to the host computer  100  is not the magnetic tape library device  130  but magnetic tape devices  131   a ,  131   b . In the magnetic tape library device  130  (see  FIG. 1 ) and the virtual tape device, normally a tape volume to be used is automatically mounted by the system, making it necessary to manage tape volumes. So these tape devices have a management table (e.g., a magnetic tape library management table  150 ). On the other hand, in magnetic tape devices (using cartridge type magnetic tape volumes), a tape volume to be used is manually mounted by the user. So they do not use a management table and the tape volumes are managed by the user. In such a case, too, the tape device data transferring method of this invention can be applied. Here, let us explain about a process of data transfer from a magnetic tape volume  132   a  to a magnetic tape volume  132   b.    
     The magnetic tape devices  131   a ,  131   b  in the second embodiment of this invention are just one example and this configuration shows at least one tape device with no management table for managing tape volumes. Thus, the system of the second embodiment may include a magnetic tape device  131   a  with no tape volume management table and also devices with the management table, such as a magnetic tape library device and a virtual tape device. 
     As shown in  FIG. 8 , the second embodiment has a configuration that does not use the magnetic tape library device  130  nor the virtual tape device of the first embodiment. The system configuration shown in  FIG. 8  therefore does not use on the memory  120  of the host computer  100  the magnetic tape library control program  118  and the virtual tape control program  116 , both of which are used in the system configuration of  FIG. 1 . It is also noted that magnetic disc volumes  141  of a magnetic disc device  140  do not use a magnetic tape library management table  150  nor a virtual tape management table  152 . The magnetic tape devices  131   a ,  131   b  have magnetic tape volumes  132   a ,  132   b , respectively. Constitutional parts identical with the corresponding parts shown in  FIG. 1  are assigned like reference numbers and their explanations are omitted. 
       FIG. 9  is a flow chart showing a data transfer operation in the second embodiment performed in response to a data transfer request. Unlike the first embodiment (flow chart of  FIG. 6 ), the second embodiment does not have a step S 601 . That is, there is no step to operate a management table of tape volumes that would otherwise be performed by the management information control unit  115 . 
     In response to an instruction by the input/output terminal  160 , the data transfer program  112  is executed by the CPU  110  of the host computer  100  to perform the data transfer operation. The data transfer control unit  114  checks if information about the magnetic tape volume  132  of interest is already registered (generated) in the tape device conversion table  121  (step S 602 ). If the information is not registered (No in step S 602 ), the data transfer control unit  114  newly registers information with the tape device conversion table  121 A (see  FIG. 10 ) (step S 603 ). If it is registered (Yes in step S 602 ), the step S 603  is skipped. 
       FIG. 10  shows an example of a tape device conversion table in the second embodiment. The tape device conversion table  121 A has registered therein information about tape volume names  200  of tape volumes to be data-transferred, source tape device names  201  and destination tape device names  202 . For example, registered information in a row  210 A represents a case where a magnetic tape volume  132   a  with a tape volume name VOL 001 , which is used in a source tape device name TAPE 1  of the magnetic tape devices  131   a , is transferred to a magnetic tape volume  132   b  with a tape volume name VOL 001 , which is used in a tape device name TAPE 2 . 
     Returning to  FIG. 9 , the process moves to step S 604 . Those steps identical with the corresponding ones of  FIG. 6  are assigned like reference numbers and their explanations are omitted. After the data transfer is complete, the management information control unit  115  updates information in the file registration table  151  having file locations. 
     The tape volume access processing performed when a tape volume access request is made during the data transfer operation is the same as that of the first embodiment (process flow of  FIG. 7 ). In response to an instruction by the input/output terminal  160 , the host computer  100  executes the input/output control program  113  to control an access request to a tape volume by using the tape device conversion table  121  and journal  122  even if the tape volume of interest is not managed by the management table. 
     With the above processing, it is also possible to perform a data transfer from a slow, small-capacity, old type magnetic tape volume  132   a  connected to the magnetic tape device  131   a  to a fast, large-capacity, new type magnetic tape volume  132   b  connected to the magnetic tape device  131   b . Further, this embodiment allows the data transfer to be performed without stopping transactions or without the user having to be aware of the destination/source tape volumes when accessing the tape volumes. 
     It should be further understood by those skilled in the art that although the foregoing description has been made on embodiments of the invention, the invention is not limited thereto and various changes and modifications may be made without departing from the spirit of the invention and the scope of the appended claims.