Merging incremental copies
When you make an incremental image copy by specifying FULL NO (or FULL AUTO or CHANGELIMIT) and CUMULATIVE YES, 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. merges the two incremental copies by modifying or deleting the entry for the earlier copy in the SYSIBM.SYSCOPY table. 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, 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
(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
with the LOGSORT option for recovery results in further savings in time and cost.
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.