105 lines
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105 lines
7.6 KiB
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<meta name="abstract" content="The considerations apply for opening files when sequential-only processing is specified. If the system determines that sequential-only processing is not allowed, a message is sent to the program to indicate that the request for sequential-only processing is not being accepted; however, the file is still opened for processing." />
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<title>Open considerations for sequential-only processing</title>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Open considerations for sequential-only processing</h1>
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<div><p>The considerations apply for opening files when sequential-only
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processing is specified. If the system determines that sequential-only processing
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is not allowed, a message is sent to the program to indicate that the request
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for sequential-only processing is not being accepted; however, the file is
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still opened for processing. </p>
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<div class="p"> <ul><li>If the program opened the member for output only, and if SEQONLY(*YES)
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was specified (number of records was not specified) and either the opened
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member is a logical member, a uniquely keyed physical member, or there are
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other access paths to the physical member, SEQONLY(*YES) is changed to SEQONLY(*NO)
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so the program can handle possible errors (for example, duplicate keys, conversion
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mapping, and select/omit errors) at the time of the output operation. If you
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want the system to run sequential-only processing, change the SEQONLY parameter
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to include both the *YES value and number of records specification.</li>
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<li>Sequential-only processing can be specified only for input-only (read)
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or output-only (add) operations. If the program specifies update or delete
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operations, sequential-only processing is not allowed by the system.</li>
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<li>If a file is being opened for output, it must be a physical file or a
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logical file based on one physical file member.</li>
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<li>Sequential-only processing can be specified with commitment control only
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if the member is opened for output-only.</li>
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<li>If sequential-only processing is being used for files opened with commitment
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control and a rollback operation is performed for the job, the records that are
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in the job's storage area during the rollback operation are not written to
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the system storage area and never appear in the journal for the commitment
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control transaction. If no records were ever written to the system storage
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area prior to a rollback operation being performed for a particular commitment
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control transaction, the entire commitment control transaction is not reflected
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in the journal.</li>
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<li>For output-only, the number of records specified to be moved as a unit
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and the force ratio are compared and automatically adjusted as necessary.
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If the number of records is larger than the force ratio, the number of records
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is reduced to equal the force ratio. If the opposite is true, the force ratio
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is reduced to equal the number of records.</li>
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<li>If the program opened the member for output only, and if SEQONLY(*YES)
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was specified (number of records was not specified), and duplicate or insert
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key feedback has been requested, SEQONLY(*YES) will be changed to SEQONLY(*NO)
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to provide the feedback on a record-by-record basis when the records are inserted
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into the file.</li>
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<li>The number of records in a block will be changed to one if all of the
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following conditions are true: <ul><li>The member was opened for output-only processing.</li>
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<li>No override operations are in effect that have specified sequential-only
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processing.</li>
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<li>The file being opened is a file that cannot be extended because its increment
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number of records was set to zero.</li>
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<li>The number of bytes available in the file is less than the number of bytes
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that fit into a block of records.</li>
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</ul>
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</li>
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</ul>
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</div>
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<div class="p">The following considerations apply when sequential-only processing is not
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specified and the file is opened using the Open Query File (OPNQRYF) command.
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If these conditions are satisfied, a message is sent to indicate that sequential-only
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processing will be performed and the query file is opened. <ul><li>If the OPNQRYF command specifies the name of one or more fields on the
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group field (GRPFLD) parameter, or OPNQRYF requires group processing.</li>
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<li>If the OPNQRYF command specifies one or more fields, or *ALL on the UNIQUEKEY
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parameter.</li>
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<li>If a view is used with the DISTINCT option on the SQL SELECT statement,
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then SEQONLY(*YES) processing is automatically performed.</li>
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</ul>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rbafoseqop.htm" title="If your program processes a database file sequentially for input only or output only, you might be able to improve performance using the sequential-only processing (SEQONLY) parameter on the Override with Database File (OVRDBF) or the Open Database File (OPNDBF) command.">Sequential-only processing of database files</a></div>
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</div>
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<div class="relconcepts"><strong>Related concepts</strong><br />
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<div><a href="rbafoopnqf.htm" title="The Open Query File (OPNQRYF) command is a control language (CL) command that allows you to perform many data processing functions on database files. These topics discuss how to create a query using the OPNQRYF command, how to specify parameters for its major functions, and how to use it with your high-level language program.">Use Open Query File (OPNQRYF) command</a></div>
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