Reusing image copy data sets

DBRC enables you to reuse old image copy data sets. The REUSE parameter of the INIT.DBDS command, in addition to enabling you to define image copy data sets for future use, enables DBRC to reuse image copy data sets. To reuse the image copy data set means that the same name, volumes, and physical space are used for the new image copy.

Restriction: DFSMSdss fast replication, as invoked by the Database Image Copy 2 utility, does not support the REUSE parameter. Consequently, the information in this topic does not apply for fast replication image copies.

A run of one of the IMS image copy utilities automatically reuses the oldest image copy data set for a DBDS or area with the REUSE attribute when all of the following conditions are met:

A number of image copy data sets equal to the current GENMAX value are recorded in the RECON data set. To see the current GENMAX value, use the LIST.DBDS command.
The Database Image Copy utility or Online Database Image Copy utility used all image copy data sets for this DBDS. None of the image copy data sets is available.
The oldest image copy is beyond the recovery period.
A run of one of the IMS image copy utilities automatically uses an available image copy if one exists. If GENMAX has been reached and the oldest image copy is beyond the recovery period or there is no recovery period, the oldest image copy data set is made available.

When you use a GENJCL.IC command to generate the job for the Database Image Copy utility, the image copy data set that is to be reused is automatically selected. If the number of image copy data sets is less than the GENMAX value and all image copy data sets have been used, more image copy data sets must be defined for the DBDS or area before running the Database Image Copy utility. The number of image copy data sets should be greater than the GENMAX value if you want to use a recovery period.

The Database Image Copy 2 utility can create up to four output image copy data sets. However, if you issue a GENJCL.IC command for a DBDS defined as REUSE, DBRC generates JCL for only one or two output copies (because you can define image copy data sets for only one or two copies). If you use the GENJCL.IC command for the Database Image Copy 2 utility to process a DBDS defined as REUSE and you want more than two output copies, modify the generated JCL before you run the job.

DBRC generates JCL so that the oldest DASD data set is always used for output for the image copy. DBRC has the same capability with tape volumes. However, you need to analyze your existing tape library techniques to make sure there is no conflict.