Dual Mirror Image File Support

Each IOA Access Method file can be created with dual mirror image file support. For each logical extent of the file, the IOA Access Method automatically allocates a dual extent of the same size. The name of the dual extent is identical to that of the corresponding primary extent, except for the first character of the last qualifier that is set to D instead of E (for example, prefix.dbname.Dnnn).

The dual mirror image file is not supported by Control-M/Tape.

The dual mirror image file is created if parameter DUAL in the IOA Access Method definition member is set to Y (Yes). (For more information, see the IOADBF utility in the INCONTROL for z/OS Utilities Guide.) The definition member also specifies the unit and volume names for the dual file allocation.

The IOA Access Method synchronizes the primary and dual files. All read operations are performed only from the primary file, and all write operations are performed in parallel to both files. The dual file is allocated dynamically.

For improved performance and recovery capability, different volumes must be used for the primary and dual files.

You should activate dual mirror image support for only the data component and not the index component of the IOA Access Method files.