Tuning Performance › VSAM Data Set Tuning › VSAM Processing in a Subtask

VSAM Processing in a Subtask

You can nominate VSAM I/O to be performed by a subtask rather than the System Services main task. This provides increased throughput by overlapping VSAM processing. To nominate a subtask to perform VSAM I/O, use the VSAMIO JCL parameter.

Note: Using a subtask is only useful when there is significant VSAM processing and you have a multi-CPU machine.

You can use the SHOW VSAMIO command to obtain statistics of VSAM processing.

Example

Following is an example of SHOW VSAMIO command output:

(18.51)---------------- Operator Console Services (OCS) -----------------------
show vsamio
N13A10 VSAM I/O MANAGER STATISTICS.
N13A11 MODE: DYNAMIC MOLAP: 20 MBPWAIT: 5 DSTS: 2 DSTM: 0 REQS: 173K
N13A12 TASK REQUESTS COL POL TIMES-POL NOWAIT PSWAIT PENDING
N13A13 MAIN 133K 0 2 1229 111K 11107 -
N13A13 SUB 39491 0 5 1 37542 - 0
N13A14 OLAP M/T S/T
N13A15 0 0 7300
N13A15 1 21145 1448
N13A15 2 1229 237
N13A15 3 0 22
N13A15 4 0 2
N13A15 5 0 1
N11907 *END*

==> show vsamio

More information:

Product Region JCL Parameters