Start of changeCICS VSAM Transparency for z/OS, Version 1.2


The dual mode facility (DMF)

The primary purpose of the dual mode facility (DMF) is to help identify errors in data set mapping, especially where re-engineering is achieved using user-written exits. This normally occurs during the data verification phase of data migration. You can also use DMF to support application testing.

When DMF is activated, VSAM calls from application programs are processed by CICS® VT against both VSAM data and DB2® data. The data areas, return codes, and reason codes are automatically compared. If any difference is detected in a batch program, an abend occurs. If any difference is detected in a CICS program, the action taken by CICS VT depends on the value of the ERRORACT DST option.

The checking performed by DMF varies according to the type of VSAM call as follows:

The return code and reason code are compared first, followed by the data areas. If DMF detects any difference, diagnostic data is produced and the application program is abnormally terminated.

You should not use DMF in a production capacity.

The following terminology is used in this chapter:


Concept topic


Last updated: November 9, 2012 20:42:42
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