Merging incremental copies

BMC AMI Copy allows you to choose whether to merge a new incremental copy with the most recent prior incremental copy.

The RESETMOD and CUMULATIVE options provide this choice.

Important

When RESETMOD NO is used to make incremental copies, BMC AMI Copy sets SHRLEVEL in SYSIBM.SYSCOPY to N for SHRLEVEL CHANGE copies or M for SHRLEVEL REFERENCE copies. However, Db2 treats both N and M as SHRLEVEL CHANGE.

Related topics

Managing-table-space-incremental-image-copies

RESETMOD

Resetting-modified-page-indicators-RESETMOD

When you make an incremental image copy by specifying FULL NO (or FULL AUTO or CHANGELIMIT) and CUMULATIVE YES, BMC AMI Copy looks in SYSIBM.SYSCOPY to see if the most recent copy for this table space is an incremental copy made with the RESETMOD NO option. If it is, the new incremental copy includes all pages of the earlier incremental copy. BMC AMI Copy merges the two incremental copies by modifying or deleting the entry for the earlier copy in the SYSIBM.SYSCOPY table. BMC AMI Copy deletes the entry if you specify KEEP NO and modifies it if you specify KEEP YES. If you specify CUMULATIVE YES, but the most recent incremental image copy was not made with RESETMOD NO, BMC AMI Copy changes the request to CUMULATIVE NO. (For more information, see Keeping-and-recalling-merged-incremental-copies.)

This method offers several advantages. If you use it routinely, you never need more than one full image copy and one incremental copy when using BMC AMI Recover (or IBM Db2 RECOVER) to recover to the current time. The method reduces the time needed to recover and the number of copy data sets that must be managed. Because only one incremental copy is available, the recover utility requires only one tape unit for incremental copy purposes. Specifying FULL NO, RESETMOD NO, and CUMULATIVE YES also eliminates the need to run the MERGECOPY utility to produce merged incremental copies, and it reduces the time and cost required to merge incremental copies. Using BMC AMI Recover with the LOGSORT option for recovery results in further savings in time and cost.

Warning

When you use the MERGECOPY utility with RESETMOD NO CUMULATIVE YES KEEP YES incremental copies, MERGECOPY abends due to an incompatibility between BMC AMI Copy and the MERGECOPY utility. Instead of MERGECOPY, you can use the BMC AMI Recover product to correctly handle RESETMOD NO CUMULATIVE YES KEEP YES copies. For more information, see BMC AMI Recover for Db2 documentation.

An example of a disadvantage of making a merged incremental copy is that for spaces with a daily update activity of 10% or more, the time required to make the copy might be greater than the time required to make a full copy of the same space (For more details, see Optimizing-the-elapsed-time-for-an-incremental-copy). To specify that the incremental copy should include only pages changed since the last copy (that is, it should not be merged), you can use the CUMULATIVE NO option with RESETMOD NO.

 

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