Restriction: Can be specified only following a DDNAME level selector. There are some vendor supplied (and possibly in-house) applications that misrepresent the type of processing that they actually perform. This is usually the result of a general purpose I/O routine that is called by several different but related programs.
This common I/O module specifies all possible OPEN options to be ready for any possible type of request. For example, there are some vendor supplied COBOL applications that specify DYNAMIC file access in the I/O module, but one or more of the programs that call this I/O module are purely SEQUENTIAL (or purely RANDOM).
For applications that actually use SEQUENTIAL processing but specify DYNAMIC file processing, additional performance can be gained by specifying SEQUENTIAL in a LEVEL selector that matches that application.
For example, if you have purchased a vendor supplied MRP, payroll, or other package that uses SEQUENTIAL processing, but was written with DYNAMIC specified in the file declaration, you should select that application (by program name/ddname) and specify SEQUENTIAL, as shown below.
. . .
. . .
PROGRAM=MRP0001
DDNAME=ORDERS
SEQUENTIAL
. . . .
. . . .
This forces the dynamic buffering calculation to be performed as if the OPEN was purely SEQUENTIAL. This usually results in more data buffers, which improves performance for the sequential processing.
Specifying SEQUENTIAL overrides the automatic assignment of random files to LSR pools.
There are no operands for SEQUENTIAL.
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