Reusing image copy data sets

The REUSE keyword of the INIT.DBDS command, in addition to allowing you to define image copy data sets for future use, allows DBRC to reuse image copy data sets. To reuse the image copy data set means that DBRC uses the same name, volume, physical space, and record in the RECON data set for the new image copy data set as for the old one.

When you run one of the image copy utilities, IMS automatically reuses the oldest image copy data set for a DBDS or area, if it can, when both of the following conditions are met:

• The RECON data set has records for a number of image copy data sets equal to the current GENMAX value. To see the current GENMAX value, use the LIST.DBDS command.
• The oldest image copy is beyond the recovery period.

When you use the GENJCL.IC command to generate the job for the Database Image Copy utility or Database Image Copy 2 utility, IMS automatically selects the image copy data set to be reused. If the number of image copy data sets is less than the GENMAX value, and all image copy data sets have been used, you must define more image copy data sets for the DBDS or area before running the Database Image Copy utility or Database Image Copy 2 utility. The number of image copy data sets should be greater than the GENMAX value if you want to use a recovery period.

If you do not allow IMS to reuse image copy data sets, but the GENMAX value has been reached and the RECOVPD has been exceeded, when you run the Database Image Copy utility or Database Image Copy 2 utility, DBRC selects a new image copy data set and deletes the record in the RECON data set with the oldest time stamp. IMS does not scratch the image copy data set itself. You must scratch the data set yourself or keep track of it, because DBRC is no longer aware of its existence.