VSAM Performance Enhancement › VPE Operation › VPE Rules Table › VSAM Statement

VSAM Statement

The following section explains the VSAM statement.

VSAM	[POOL=n]

 [,BUFFRLOC=ABOVE|BELOW]
 [,SIS=NO|YES]
 [,VSAMREC=NO|YES]
 [,TGTBUF=nnM]
 [,MINBUF=nnM]
 [,MINRESV=nnnK]

The VSAM statement sets global system options. There can be at most one VSAM statement. It can be omitted if you want. These options are used to tune VPE. Like the SYSOPT statement, these options set the default values for your system. They are global in nature and apply to all jobs, steps, and VSAM files unless overridden by more specific rules or special VPE DD cards.

POOL=n

Specifies the LSR pool number which VPE is to use for I/O buffers. The default value is 3.

This is the pool number and not the number of pools. VSAM supports 16 LSR pools for data components and 16 for index components. Both sets of pools are numbered 0 through 15. POOL= specifies which of these pairs of pools are to be used.

BUFFRLOC=ABOVE|BELOW

Specifies from where the LSR buffer space is to be obtained, above or below the 16 Mb line.

Note: In either case, a VPE RULE statement or special VPE DD statement can override this global value for the data sets affected by them.

SIS=NO|YES

SIS=YES directs VPE to globally turn on VSAM's Sequential Insert Strategy (SIS) for all applicable ACBs.

SIS=NO (the default) directs VPE to not do so.

VSAMREC=NO|YES

VSAMREC=YES directs VPE to globally produce the VSAM Recommendations Report for every VSAM data set open.

VSAMREC=NO (the default) directs VPE to not do so.

Note: A VPE RULE statement or special VPE DD statement can override this global value for the data sets affected by them.

TGTBUF=nnM

directs VPE to attempt to obtain the specified number of megabytes for the VSAM I/O buffer. If VPE cannot obtain this much space, it reduces the request until the space request succeeds, or until the minimum buffer size is reached (see the MINBUF=nnM parameter below). The default target buffer size is 9 Mb if the LSR buffers are above the 16 Mb line, and 4 Mb if they are below it.

MINBUF=nnM

Works in conjunction with the ABENDNOMIN=YES parameter of a RULE statement. MINBUF=nnM specifies the minimum VSAM I/O buffer size which is acceptable. The default is zero. If a nonzero value is specified for MINBUF=nnM and ABENDNOMIN=YES is specified, VPE abends the job step if the minimum buffer space cannot be obtained.

MINRESV=nnnnK

Specifies the minimum amount of memory to reserve below the 16 Mb line for the application to use. The default setting is 300K. VPE does not enhance sequential file buffering if this amount of memory is not available. When LSR buffers are being acquired below the 16 Mb line, this value reduces the size of the VSAM I/O buffers if this amount of space is not available.