Patent Abstract:
A database server helps to streamline the retrieval of LOB values by deciding to send a locator in replacement of the LOB value, or the LOB value itself, depending upon the specific LOB value being retrieved. A threshold value is determined in a fetch query, and the LOB sizes below that threshold are sent as values in a corresponding fetch response, and the lengths above are sent as locators in the fetch response. Indicators are inserted in a fetch parameter of the response to inform the receiving client the form of retrieval that was used for each requested LOB value being returned.

Full Description:
PRIORITY CLAIM  
         [0001]    The present application claims the priority of Canadian patent application, Serial No. 2,419,982, titled “Executing A Large Object Fetch Query Against A Database,” which was filed on Feb. 26, 2003, and which is incorporated herein by reference.  
         FIELD OF THE INVENTION  
         [0002]    The present invention relates in general to database management systems, and in particular to a system and associated method for executing a large object fetch query against a database.  
         BACKGROUND OF THE INVENTION  
         [0003]    With the advent of Web application servers, the use of large objects (LOBs) in database systems is increasing. In many cases, these LOBs are used to store session state: serialized Java objects or other structures known to applications accessing the database systems. Once requested, retrieval of the LOBs from database servers to the application in a performance efficient fashion is critical.  
           [0004]    Typically, these LOB objects are relatively small (i.e., less than 10 K), but on occasion they can be quite large (i.e., greater than 100 K). To take into account future growth, database administrators typically define quite large sizes (i.e., greater than 1 GB) for LOB columns of the database. If the database administrator knew these objects would never have the possibility of becoming LOBs, the column could be defined as long varchar for bit data. It is assumed that defining columns as LOBs indicates the corresponding objects will occasionally have very large values (i.e. considered as LOBs). There currently exists two methods for retrieving LOBs from the database, with current architectures: by defining a locator, or by asking for the LOB value.  
           [0005]    The locator approach can have an advantage that only a handle flow is returned from the database server to the application. The actual LOB value remains on the database server until the application is ready to fetch the LOB value or any part of the LOB value. A disadvantage to the locator approach, especially in the case where the LOBs are relatively small, can be that an additional network flow to the database server is required to retrieve each LOB. Therefore, by always specifying locators in response to the data request, system drivers are forcing a second trip to the database server to retrieve the value of every LOB, thus exacting a potential system performance penalty.  
           [0006]    An alternative approach for LOB retrieval is that of fetching the LOB value up front. LOB value retrieval can be more appropriate for the case of small LOBs, but can consume a considerable amount of memory on the client for large LOBs, especially if the application was only interested in a small portion of the large LOB. One disadvantage of the LOB retrieval method is that by always specifying the value to be returned, the client of the application can be occasionally hit by a very large LOB, which can force a significant amount of memory to be used at the client for LOB buffering. Further, the application may not require the entire LOB, and as a result may cause inefficiencies in client memory allocation and utilization.  
           [0007]    Consequently, with current architectures, the application (or for example a JDBC/ODBC driver) must make the decision up front to retrieve the LOB either by the locator or by value. This decision is typically made by the driver without assistance from the application; the driver usually selects the locator approach. The locator approach can be the recommended approach for JDBC implementers to use. In either case, the decision for retrieval type is made at the client with possible knowledge of a defined maximum length of the column (which is often quite large), but without knowledge of the actual length of the particular resident LOB value in the corresponding database field.  
           [0008]    What is therefore needed is a system and associated method that enable the database management system to make a dynamic decision for sending either the LOB locator or the LOB value in the fetch response, depending upon the actual value of the LOB in comparison to the threshold value. The need for such system and method has heretofore remained unsatisfied.  
         SUMMARY OF THE INVENTION  
         [0009]    The present invention satisfies this need, and presents a system, a computer program product, and an associated method (collectively referred to herein as “the system” or “the present system”) for executing a large object fetch query against a database.  
           [0010]    A database management system DBMS (operating on a server) is adapted to receive a fetch query having a fetch request for fetching a LOB (large object). The DBMS processes each fetch request by accessing or retrieving LOB values from a database. The DBMS decides whether to return a LOB locator in place of returning a LOB value, or to return the LOB value by itself, depending upon a comparison between the specific LOB value being accessed or retrieved and a threshold value.  
           [0011]    The threshold value is associated with the fetch query and is linked to the fetch request as a threshold parameter. The LOB value or the LOB locator is returned in a fetch answer corresponding to the processed fetch request. A fetch response containing each fetch answer is returned to a client by the DBMS as a result of the fetch query. During processing of each fetch request of the fetch query, LOB values (sizes) resident in the database and below the threshold value are retrieved and returned by the DBMS to the client as LOB values in the fetch answer corresponding to the fetch request. Otherwise, LOB values (sizes) resident in the database and above the threshold value are accessed but returned by the DBMS to the client in the fetch answer as LOB locators in the fetch request of the fetch response.  
           [0012]    The use of the threshold parameter (with associated threshold value) provides a mechanism for returning LOB values to the client when the LOB value is considered relatively small, and sending the LOB locators when the LOB value is considered relatively large in comparison to the threshold value. Therefore, the use of the threshold parameter of the fetch query enables the database management system to make a dynamic decision (that is, a decision made on the fly) for sending either the LOB locator or the LOB value in the fetch response. The choice of including the LOB locator or LOB value in the fetch response depends upon the actual value of the LOB in comparison to the threshold value. For example, the LOB values lower than the threshold value are sent as LOB values in columns (i.e. the fetch answers) of the fetch response, while the LOB values larger than or equal to the threshold value are sent as LOB locators in place of the LOB values.  
           [0013]    Distinct indicators are also included in the fetch response, placed in a fetch parameter. The fetch parameter is associated with the fetch response and is linked to the fetch answer, preferably one fetch parameter for each fetch answer. One of a pair of distinct indicator values is inserted in the fetch parameter for each fetch answer. This pair of distinct indicator values informs the receiving client (that is, the client receiving the fetch response) which form of access or retrieval was used for each requested LOB value being returned (via the fetch answers in the fetch response). As a result of the query received by the database management system (operating on the server), the fetch parameter uses these distinct indicator values to help inform the client of the form of access/retrieval present in the fetch response.  
           [0014]    In an embodiment of the present invention, a method is provided for directing a database management system to execute a fetch query against a database used for storing LOB (Large Object) values and associated LOB locators. This fetch query is adapted to contain at least one LOB fetch request. This method includes the steps of:  
           [0015]    receiving the fetch query,  
           [0016]    accessing a selected LOB value stored in the database,  
           [0017]    comparing the selected LOB value with the predefined threshold value, and  
           [0018]    returning a fetch response having a LOB fetch answer corresponding to the LOB fetch request according to one of a pair of return operations.  
           [0019]    The fetch query includes a threshold parameter associated with the LOB fetch request and the threshold parameter has a predefined threshold value. The selected LOB value corresponds to the LOB fetch request of the fetch query. The first return operation of the pair returns the selected LOB value in the LOB fetch answer if the compared LOB value is less than the predefined threshold value. A second return operation of the pair returns the LOB locator in the LOB fetch answer if the compared LOB value is greater than the threshold value.  
           [0020]    In another embodiment of the present invention, a computer program product is provided that has a computer-readable medium tangibly embodying computer executable instructions for directing a database management system to execute a fetch query against a database used for storing LOB (Large Object) values and associated LOB locators. The fetch query is adapted to contain at least one LOB fetch request. The computer program product comprises: computer readable code for receiving the fetch query, computer readable code for accessing a selected LOB value stored in the database, computer readable code for comparing the selected LOB value with the predefined threshold value, and computer readable code for returning a fetch response having a LOB fetch answer corresponding to the LOB fetch request according to one of a pair of return operations.  
           [0021]    As described earlier, the fetch query includes a threshold parameter associated with the LOB fetch request and the threshold parameter has a predefined threshold value. The selected LOB value corresponds to the LOB fetch request of the fetch query. The first return operation of the pair returns the selected LOB value in the LOB fetch answer if the compared LOB value is less than the predefined threshold value. A second return operation of the pair returns the LOB locator in the LOB fetch answer if the compared LOB value is greater than the threshold value.  
           [0022]    In yet another embodiment of the present invention, there is provided an article comprising a computer-readable signal-bearing medium usable on a network. This article also comprises means in the medium for directing a database management system to execute a fetch query against a database used for storing LOB (Large Object) values and associated LOB locators. The fetch query is adapted to contain at least one LOB fetch request. This article comprises: means in the medium for receiving the fetch query, means in the medium for accessing a selected LOB value stored in the database, means in the medium for comparing the selected LOB value with the predefined threshold value, and means in the medium for returning a fetch response having a LOB fetch answer corresponding to the LOB fetch request according to one of a pair of return operations.  
           [0023]    As described earlier, the fetch query includes a threshold parameter associated with the LOB fetch request and the threshold parameter has a predefined threshold value. The selected LOB value corresponds to the LOB fetch request of the fetch query. The first return operation of the pair returns the selected LOB value in the LOB fetch answer if the compared LOB value is less than the predefined threshold value. A second return operation of the pair returns the LOB locator in the LOB fetch answer if the compared LOB value is greater than the threshold value.  
           [0024]    In still another embodiment of the present invention, a database management system is provided for executing a fetch query against a database used for storing LOB (Large Object) values and associated LOB locators. The fetch query is adapted to contain at least one LOB fetch request. The database management system comprises: means for receiving the fetch query, means for accessing a selected LOB value stored in the database, means for comparing the selected LOB value with the predefined threshold value, and means for returning a fetch response having a LOB fetch answer corresponding to the LOB fetch request according to one of a pair of return operations.  
           [0025]    As described earlier, the fetch query includes a threshold parameter associated with the LOB fetch request and the threshold parameter has a predefined threshold value. The selected LOB value corresponds to the LOB fetch request of the fetch query. The first return operation of the pair returns the selected LOB value in the LOB fetch answer if the compared LOB value is less than the predefined threshold value. A second return operation of the pair returns the LOB locator in the LOB fetch answer if the compared LOB value is greater than the threshold value.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]    The various features of the present invention and the manner of attaining them will be described in greater detail with reference to the following description, claims, and drawings, wherein reference numerals are reused, where appropriate, to indicate a correspondence between the referenced items, and wherein:  
         [0027]    [0027]FIG. 1 is a schematic illustration of an exemplary server database system in which a large object fetch system of the present invention can be used;  
         [0028]    [0028]FIG. 2 is a diagram of an exemplary client database system of FIG. 1 in which a large object fetch system of the present invention can be used;  
         [0029]    [0029]FIG. 3A is a diagram of a data structure of the database of FIG. 1;  
         [0030]    [0030]FIG. 3B is a diagram of a response structure of the system of FIG. 1;  
         [0031]    [0031]FIG. 4 is a block diagram illustrating a method of an operation of a database management system of FIG. 1;  
         [0032]    [0032]FIG. 5 is a process flow chart illustrating the method of a server fetch operation of the database management system of FIG. 4; and  
         [0033]    [0033]FIG. 6 is a process flow chart illustrating the method of a companion client fetch operation of the server fetch operation of FIG. 5.  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0034]    The following detailed description of the embodiments of the present invention does not limit the implementation of the invention to any particular computer programming language. The present invention may be implemented in any computer programming language provided that the OS (Operating System) provides the facilities that may support the requirements of the present invention. An embodiment is implemented in the C or C++ computer programming language (or other computer programming languages in conjunction with C/C++). Any limitations presented would be a result of a particular type of operating system or computer programming language and would not be a limitation of the present invention.  
         [0035]    The embodiments of the present invention provide a method (as shown in FIGS. 4, 5,  6 ), a data processing system (FIGS. 1 and 2), and/or a computer program product (not depicted), and/or an article (not depicted) for dynamic processing of a fetch query in a server database system. The server database system is coupled to a database adapted to store LOB values. It will be appreciated by those skilled in the art, that the article can be a signal-bearing medium for transporting computer readable code to a data processing system over a network, in which the code can be used to implement the method.  
         [0036]    It will also be appreciated, by those skilled in the art, that the computer program product comprises a computer readable medium having computer executable code for directing a data processing system to implement the method. The computer program product can also be called a computer-readable memory, in which the memory can be a CD, floppy disk or hard drive or any sort of memory device usable by a data processing system. It will also be appreciated by those skilled in the art, that a data processing system may be configured to operate the method. The method may be operated either by use of computer executable code residing in a medium or by use of dedicated hardware modules, also generally or generically known as mechanisms or means, which may operate in an equivalent manner to the code which is well known in the art.  
         [0037]    [0037]FIG. 1 shows a server database system  100  comprising a server data processing system  102  having a memory  108  tangibly embodying a database management system (DBMS)  116 , a collection of tables  120  having data  122 , and a query  118  for instructing the DBMS  116  to interact with the tables  120 . It will be appreciated that the collection of tables  120  may be included collectively as a single database, and that the database may be stored in the memory  108 , or alternatively may be stored in memories of a plurality of distributed data processing systems (not depicted) which may be interconnected by a network (not depicted).  
         [0038]    The DBMS  116  is a computerized information storage and retrieval system. For example, a relational database management system (RDBMS) is a type of the DBMS  116  that stores and retrieves the data  122  organized as tables  120 . Each of the tables  120  comprises rows  300  and columns  302  (see FIG. 3A) of data  122 . The database of the server database system  100  will typically have many tables  120  and each table  120  will typically have multiple rows  300  and multiple columns  302 .  
         [0039]    The DBMS  116  can be designed to store data  122  having a variety of data types. For example, the DBMS  116  may have the capability of storing and retrieving data  122  having standard data types, such as integers and characters, as well as non-standard data types, including very large data objects (LOBs). It is noted that typical DBMSs  116  can represent text, voice, and image data as LOB types. Exemplary applications  217  (see FIG. 2), server database system  100 , and client database system  200  may involve multimedia applications for the World Wide Web; medical care applications (e.g., X-rays, MRI imaging, and EKG traces); and geographical, space, and exploration systems (e.g., maps, seismic data, and satellite images).  
         [0040]    The memory  108  of the server database system  100  may include volatile and non-volatile memory such as but not limited to RAM (random Access memory) and/or ROM (read-only memory). Also embodied in the memory  108  is an operating system (not depicted) which may be a program that executes on the server data processing system  102  for running other computer executable programs (such as but not limited to the DBMS  116 ).  
         [0041]    Operating systems perform basic tasks, such as recognizing input/output from input/output interface modules  110  (for example coupled to a keyboard and display screen), keeping track of files and directories on a disk in the memory  108 , and controlling other peripheral devices such as but not limited to disk drives and printers. The memory  108  is operationally coupled to a CPU (Central Processing Unit)  104 , and the input/output interface modules  110  via a bus  106 .  
         [0042]    Operationally coupled to the input/output interface modules  110  are input/output devices (such as a mouse and display unit), and persistent memory units (such as a hard drive, floppy drive). A communication interface  112  is used by the server database system  100  to communicate with the Client Database System  200 .  
         [0043]    [0043]FIG. 2 shows the client database system  200  in greater detail. Components  202  through to  212  of FIG. 2 are generally identical to the corresponding components  102  through to  112  of FIG. 1, as is known in the art. A database system client  216  (alternately referenced as client  216 ) is a computer executable program that is a companion program to the DBMS  116  program, as is known in the art. The client  216  coordinates the queries  118  and responses  119  of the applications  217  to and from the server database system  100 . It is possible that hardware components of the server database system  100  (components  102 - 112 ) may be the same physical hardware components of the client database system  200  (corresponding components  202 - 212 ), which for simplicity of discussion are depicted here as separate systems.  
         [0044]    Accordingly, FIGS. 1 and 2 show an example client-server system made up of the server database system  100  and the client database system  200 , where the client applications  217  with the client  216  can reside on the client computer (not shown) and the server application (DBMS  116 ) can reside on the server computer (not shown). The client database system  200  and the server database system  100  are connected by the communication interface  212 , such as but not limited to a local area network (LAN).  
         [0045]    In operation of the client-server system, the client  216  sends the request for data  122  (for example in the form of the database query  118 ) to the DBMS  116 . The DBMS  116  processes each of the queries  118  to retrieve data  122  from the tables  120 , and returns an answer set in the form of a response  119 . The retrieved data  122  can include LOB data (i.e., data having a LOB data type).  
         [0046]    [0046]FIG. 3, which is comprised of FIGS. 3A and 3B, illustrates an exemplary data and response structure. In response to the query  118  from the application  217 , the client database system  200  contacts the server database system  100 . The response  119  to the query  118  may contain LOB data  122 . Returning the response  119  to the client database system  200  can involve returning the row  300  of data  122  having both standard and non-standard data types.  
         [0047]    An exemplary row  300  may have columns  10 ,  20 , and  30 , with columns  10  and  30  containing data  122  having standard data types (e.g., integers or characters). Column  20  could contain data having a non-standard data type (e.g., LOB data that consumes two megabytes of space in the tables  120 ). When the row  300  containing these three columns  302  is transmitted from the server database system  100  to the client database system  200 , the data  122  can be transmitted sequentially.  
         [0048]    Therefore, the client database system  200  first receives the column  10  of data  122  having the standard database data type, receives the column  20  of data  122  having the non-standard data type, and then receives the column  30  of data  122  having the standard database data type. These columns  302  of data  122  can be stored in a temporary storage location of the memory  208  and then moved to the long-term storage of the memory  208  of the application  217 .  
         [0049]    Referring to FIG. 3B, the response  119  has a data structure including an inline flag  50  and an inline LOB threshold value  60 , as further described below. These flag  50  and threshold value  60  are used as fetch parameters in the query  118  and the response  119 . The response  119  also has a header  40 . It is recognized that the query  118  has a similar format to the response  119 , including row  300 , columns  302 , the inline flag  50 , the inline LOB threshold value  60 , and the header  40 . The similarity in format of the query  118  and response  119  is typified by the database system client  216  being the computer executable program that is the companion program to the DBMS  116  program. Further, it is recognized that the queries  118  and the responses  119  can contain more than one row  300 , if desired.  
         [0050]    [0050]FIG. 4 shows the computer readable memory  108  of FIG. 1. Stored in the memory  108  are operations S 310  of the DBMS  116  of FIG. 1. The operations S 310  process a series of requests or queries  118  (see FIG. 1) received from the client  216  of FIG. 2. Within the DBMS  116  there is contained a module  117  or unit of executable computer programmed instructions comprising the operations S 360  to S 370  for directing the CPU  104  to manage the table  120 . The CPU  104  manages the table  120  by creating and transmitting the response  119  as a base data object with the header  40  (see FIG. 3B). For example, operation S 360  receives the query  118 . Operation S 362  parses the query  118 .  
         [0051]    Operation S 364  creates the data base object. Operation S 366  completes the columns  302  of the base data object  119  including the inline flag  50  and the inline LOB threshold value  60 . Operation S 368  returns the base data object in a return buffer (not shown) for transmission to the client database system  200  as the response  119 . Operation S 370  inquires if there is another query  118  present for processing by the DBMS  116 .  
         [0052]    In the client-server environment as shown in FIGS. 1 and 2, each fetch query  118  is sent from the client database system  200  to the server database system  100 . The server database system  100  can respond to the fetch queries  118  using a predefined protocol, such as a distributed relational database architecture (DRDA) single-row fetch protocol or a DRDA limited block fetch protocol.  
         [0053]    Those skilled in the art will recognize that the DRDA protocols discussed herein are not intended to limit the present invention. Indeed, those skilled in the art will recognize that other alternative protocols may be used without departing from the scope of the present invention. For example, the single-row fetch protocol returns each response  119  with either zero rows  300  or  1  row of an answer set (such as but not limited to containing columns  10 ,  20 ,  30 , flags  50 , and thresholds  60 ). For example, the limited block fetch protocol returns zero to N rows of the answer set for each query  118 .  
         [0054]    Generally, the variable N is the number of rows that can fit into a query block, wherein the query block is the return buffer that contains the formatted rows  300  of the answer set. It is recognized that the client database system  200  and the server database system  100  may negotiate the return buffer size, and that the answer set rows  300  may be returned to the client database system  200  as a data object. It is also recognized that the server database system  100  can choose the fetch protocol, or the client database system  200  sent instructions associated with the query  118  to use a predefined fetch protocol, e.g., DRDA single row fetch protocol.  
         [0055]    It will be appreciated that other operations can be included in the operations S 310  as is known in the art. Further, it will be appreciated that the instructions of the module  117  may be implemented in any computer programming language and translated into processor-readable instructions or code for execution by the CPU  104  of the server data processing system  102 . In an alternative embodiment, it may be appreciated that operations S 360  to S 370  may reside in another programmed module (not shown) which operates independently of the DBMS  116 . These operations correspond to client queries  118 , and a non-exhaustive list of these operations would comprise such as but not be limited to connecting to the tables  120 , compiling an SQL statement, fetching data  122 , inserting data  122 , updating data  122 , etc.  
         [0056]    [0056]FIGS. 3B and 5 show the details of one of the operations S 310  that corresponds to the fetch query  118 . For this example, it is assumed that operation S 364  corresponds to a particular fetch query  118  to retrieve data  122  from the table  120 , where one or more columns  302  contains LOB data  122 . Prior to making the fetch query  118  to the server database system  100 , the client  216  presets the inline LOB flag  50  for querying a LOB value, and presets the inline LOB threshold value  60  to a value such as but not limited to 10,000 bytes.  
         [0057]    This flag  50  and threshold value  60  alter the fetch processing of the DBMS  116  as further described below. Referring again to FIG. 5, as the server database system  100  is processing operation S 364 , the operation S 364  loops through each of the columns  302  in the answer set for each row  300  of the answer set represented in the response  119 . The server database system  100  retrieves the values of data  122  from the database tables  120 , and binds them out as quantities in the response  119  and through the communication interface  112  for delivery to the client database system  200 .  
         [0058]    Operation S 402  represents the start of processing for each row  300  of the answer set. In operation S 404 , the large object fetch system determines whether the column  302  represents a LOB value. If the column  302  does not represent a LOB value, operation S 406  could perform a conventional bind out process. If the column  302  does represent a LOB value, the large object fetch system proceeds to operation S 408 . The large object fetch system determines in operation  408  whether the inline LOB flag  50  is set.  
         [0059]    If the inline LOB flag  50  is not set for this LOB column  302 , traditional LOB bind out occurs at operation S 410 . If the inline LOB flag  50  is set for this LOB column  302 , the flag  50  is set as a fetch LOB request. Operation S 412  determines if the LOB size for this column  302  is less than or equal to the inline LOB threshold  60  specified for this column  302 . If the size is less than or equal to the inline LOB threshold  60 , a first binding operation S 416  is executed which places an inline LOB indicator in the flag  50  of the response  119 . This inline LOB indicator verifies the presence of the LOB value as a return quantity in the respective column  302  of the base data object. The large object fetch system then places the LOB data value inline in the response  119  being sent to the client database system  200 .  
         [0060]    Alternatively, if operation S 412  indicates the LOB size is greater than the inline LOB threshold  60 , then a second binding operation S 414  is executed which places an inline LOB locator in the flag  50 , followed by the LOB locator as the return quantity for this LOB column. All processing continues with operation S 418  that loops over all columns  302  in the row  300 .  
         [0061]    As is known in the art, the LOB locator provides only a handle flow returned from the server database system  100  to the application  217  of the client database system  200 . The actual LOB value remains on the server database system  100  until the application  217  is ready to fetch it in a subsequent query  118 . Two distinct indicators, the inline LOB indicator and the inline LOB locator indicator, return states of the flag  50 .  
         [0062]    The flag  50  is used by the client  216  to determine, on a column by column basis, transmission of the LOB value or the LOB locator in the corresponding column  302  of the response  119 . This provision allows the client database system  200  to help interpret the data  122  being sent by the server database system  100 . With these two distinct indicator return states of the flag  50 , the delivery of the LOB data  122  by either the inline LOB value or the LOB locator can be transparent to the client application  217  after the client application  217  has enabled LOB inlining.  
         [0063]    [0063]FIG. 6 details the companion client  216  operation of the corresponding operation S 364  as was detailed in FIG. 5. The client database system  200  processes the fetched values returned from the server database system  100  in the response  119  (see FIG. 3). As these values are processed, the client  216  loops through each of the columns  302  in the answer set of the response  119 . The client  216  retrieves the values of the data  122  from the communication interface  212  and binds them out to buffers provided by the user application  217  driving the query  118 .  
         [0064]    Operation S 502  represents the start of processing for each row  302  of the response  119 . The client  216  determines in operation S 504  whether the column  302  represents a LOB value. If the column  302  does not represent a LOB value in operation S 504 , operation S 506  performs traditional bind out processing, as it is known in the art.  
         [0065]    For the LOB value, operation S 508  determines whether the inline LOB indicator is present in the flag  50 . If true, the data  122  immediately following the inline LOB indicator is perceived by the client  216  as the inline LOB value, and this data  122  is bound out to the client application  217  in operation S 510 .  
         [0066]    If the inline LOB indicator is not present in the flag  50 , operation S 512  checks for the inline LOB locator indicator in the flag  50 . If the inline LOB locator indicator is present, the data  122  following is perceived by the client  216  as the LOB locator and that data  122  is bound out to the client application  217  in operation S 514 . If neither of these distinct indicators were present in the respective column  302  of the response  119 , then operation S 516  would perform traditional LOB bind out as it is known in the art. The operation continues at block S 518  that loops over all columns  302  in the row  300 . The LOB indicator and the LOB locator are considered distinct return states of the flag  50  (i.e. fetch parameter).  
         [0067]    Accordingly, in view of the above, the use of distinct indicators in the flags  50  of the response  119  provides a mechanism by which the server database system  100  can make a dynamic decision of sending either a LOB locator or the inline LOB value in the response  119 . This decision depends upon the specific value of the LOB in comparison to the threshold value  60 .  
         [0068]    Consequently, the LOB values below the threshold  60  are sent as values in the columns  302  of the response  119 , while the LOB values above the threshold  60  are sent as locators. The flag  50  uses the distinct indicator values to help inform the client  216  of the form of retrieval present in the response  119  as a result of the query  118 . It is recognized that the flags  50  and/or the thresholds  60  may be stored/read in the header  40  (see FIG. 3A, 3B), in the columns  302  as inline values, or a combination thereof. Further, it is recognized that default threshold values  60  can be used for each LOB by the server database system  100  and/or a single threshold value  60  can be used for more than one column  302  for comparison against multiple LOB values requested in the query  118 .  
         [0069]    In an alternative embodiment, there is provided a computer program product having a computer-readable medium tangibly embodying computer executable instructions for directing a data processing system to implement any method as previously described above. It will be appreciated that the computer program product may be a floppy disk, hard disk or other medium for long term storage of the computer executable instructions.  
         [0070]    It will be appreciated that variations of some elements are possible to adapt the invention for specific conditions or functions. The concepts of the present invention can be further extended to a variety of other applications that are clearly within the scope of this invention. Having thus described the present invention with respect to preferred embodiments as implemented, it will be apparent to those skilled in the art that many modifications and enhancements are possible to the present invention without departing from the scope and spirit of the present invention.

Technology Classification (CPC): 8