DB2 Environmental Considerations

Sometimes recovery is targeted to be performed at an alternative site that is already running DB2. This is not advisable. During a disaster, your whole machine will be lost. In addition to DB2, MVS, JES, and TSO, all other system software must be recovered. Your disaster recovery plan will become needlessly complex if you plan to recover to an existing system. Reconfiguring software that is already operational usually is more difficult than bringing everything up from scratch.

NOTE

Consider using the BACKUP SYSTEM and RECOVER SYSTEM utilities to help simplify the backup and recovery of you DB2 subsystem and applications for disaster recovery.

If you insist on a plan to recover to a DB2 subsystem that already exists, remember the following. All databases, table spaces, tables, and indexes must be created at the remote site. This could be performed either at the time of the disaster (which is complex and error-prone ) or before the disaster (which is easy but consumes resources). With either option, all DB2 objects must exist before the image copy data sets can be restored. This can be accomplished only by using the DSN1COPY service aid with the OBIDXLAT option.

You should maintain a comprehensive report that lists the DBID for each database, the PSID for each table space, and the OBID for each table in both DB2 subsystems. ( DBID s, PSID s, and OBID s identify each object to DB2 and are stored in the DB2 Catalog.) A query to produce this report follows :

 SELECT   S.DBNAME, S.DBID, S.NAME, S.PSID,          T.CREATOR, T.NAME, T.OBID FROM     SYSIBM.SYSTABLESPACE   S,          SYSIBM.SYSTABLES       T WHERE    S.DBNAME = T.DBNAME AND      S.NAME   = T.TSNAME AND      T.TYPE   = 'T' ORDER BY S.DBNAME, S.DBID, S.NAME, S.PSID, T.CREATOR, T.NAME; 

A QMF form to create a formatted report using this query is presented in Listing 38.2. The report generated by this query should be sent to the remote site to assist with disaster recovery. The information can be used as a reference when using DSN1COPY with the OBIDXLAT option. This is the only way to accomplish recovery to a different DB2 subsystem.

Listing 38.2. QMF Form to be Used with the DBID / PSID / OBID Query

 Total Width of Report Columns: 61 NUM  COLUMN HEADING    USAGE    INDENT   WIDTH    EDIT   SEQ  1   DATABASE          BREAK1     1        8        C      1  2   DBID              BREAK1     1        4        L      2  3   TABLE_SPACE       BREAK2     1        8        C      3  4   PSID              BREAK2     1        4        L      4  5   TABLE_CREATOR                1        8        C      5  6   TABLE NAME                   1       18        C      6  7   OBID                         1        4        L      7 

Data set management techniques also must be considered . If you allocate VSAM data sets for all production table spaces and indexes, you must use AMS to create the underlying data sets before recovery at the remote site. If you use STOGROUP s, though, the data sets are allocated when the table spaces and indexes are created.