VSAM dynamic access read option VSAMDYNAMICDIR

To change the dynamic access method of VSAM to a direct read-by-key request to the VSAM engine, you must specify the COBOL runtime option VSAMDYNAMICDIR. This alternate logic path takes advantage of IBM®'s hardware disk systems that make use of zHyperLink. zHyperLink improves application response time, which cuts I/O-sensitive workload response times significantly. If you do not change the dynamic access method, the default runtime behavior is to point to a record by key and then read records sequentially.

Note: You can take advantage of zHyperLink by changing the dynamic access method of VSAM. If you do not have zHyperLink installed, do not use VSAMDYNAMICDIR. To determine if you have zHyperLink available, see zHyperLink I/O in the IBM z/OS® documentation.

Important: You can control which applications make use of this option by following the instructions in Building IGZUOPT and IGZQUOPT runtime option control block.

To use this feature, create the IGZUOPT (for AMODE 31) or IGZQUOPT (for AMODE 64) COBOL runtime option module that will use the VSAMDYNMAICDIR=ON option.

When the IGZUOPT or IGZQUOPT module is built, specify the VSAMDYNAMICDIR option with the following syntax:

IGZXOPT VSAMDYNAMICDIR=ON | OFF

If VSAMDYNAMICDIR is not specified, the default is VSAMDYNAMICDIR=OFF.

For more details, see Building IGZUOPT and IGZQUOPT runtime option control block.

See the sample JCL IGZ5OPT in the Language Environment® sample data set .SCEESAMP to learn how to turn on VSAMDYNAMICDIR.