Use this file-level keyword to indicate that the selection and omission tests specified in the file (using select/omit specifications) are done at processing time. This keyword specifies dynamic select/omit rather than access path select/omit.
This keyword has no parameters.
As your program does input operations to a logical file with the DYNSLT keyword specified, all the records in the associated physical file are tested by the system to see if they satisfy the select/omit values. Only those records that satisfy the values are supplied to your program. The testing of each record can result in slower I/O performance, but may be more efficient than maintaining an access path for the file. This is particularly likely for files read only occasionally, especially when the physical files they are based on are updated frequently. Using dynamic select/omit is probably also more efficient for files with a high percentage of selected records.
In keyed sequence access files, an access path is created at file creation time and is maintained for the file according to the MAINT parameter on the Create Logical File (CRTLF) or Change Logical File (CHGLF) command. The DYNSLT keyword does not affect the maintenance of access paths for keyed sequence access files.
For all single-format logical files with a DYNSLT keyword, you do not need to specify key fields in order to specify select/omit fields. However, for all multiple-format logical files with a DYNSLT keyword, you do need to specify at least one key field. You can specify *NONE for this key field.
You must use the DYNSLT keyword when you want to select or omit fields and any of the following are true:
You cannot specify the DYNSLT keyword with the REFACCPTH keyword.
For a join logical file, the select/omit fields can occur in any of the physical files specified on the JFILE keyword. Use the JREF keyword in join logical files to qualify the origin of the field and resolve any ambiguities.
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