Forward recovery of versioned index spaces
Versioning occurs when the attributes of an index column have been altered. NGT Recover needs information from the header page and the directory page to recover such an index space.
The header page is always the very first page of any partition or the very first piece of a nonpartitioned index (NPI).
Page 4 will always be a directory page. If the index has been versioned several time, there may be more directory pages throughout the index.
BMC strongly recommends that you rebuild or REORG indexes with more than one directory page if you are creating image copies on a DB2 subsystem prior to DB2 Version 10. Otherwise, the recovery may fail. With DB2 Version 10, the directory pages will be written at the beginning of the image copy, insuring that the recovery will be successful.
With image copies made prior to DB2 Version 10, if a multi-data-set, nonpartitioned index contains a versioned column, the very first piece of the NPI must be included in any request to recover the NPI. NGT Recover must have at least a header page to process the recovery correctly. If the NPI was altered prior to migrating, and the index was not rebuilt or reorganized, the recovery will fail with the following error if the directory page is contained in a piece that is not included in the recovery.
BMC40855 CANNOT OBTAIN DIRECTORY PAGE INFORMATION. REQUESTED RECOVERY IS NOT POSSIBLE.
In the case of a versioned index, NGT Recover reorders the recovery request to use the correct order of DSNUM. For example, NGT Recover accepts the following command statements, but reorders the request to process DSNUM 1 first:
RECOVER INDEX (I1) DSNUM 5 RECOVER INDEX (I1) DSNUM 1