Using DFSMSdss concurrent copy

You might be able to gain improved availability by using the concurrent copy function of the DFSMSdss component of the Data Facility Storage Management Subsystem (DFSMS). To complete recovery, you can subsequently run the Db2 RECOVER utility to restore those image copies and apply the necessary log records to them.

The CONCURRENT option of COPY invokes DFSMSdss concurrent copy. The COPY utility records the resulting DFSMSdss concurrent copies in the catalog table SYSIBM.SYSCOPY with ICTYPE=F and STYPE=C or STYPE=J. STYPE=C indicates that the concurrent copy was taken of the "I" instance of the table space (which means that the instance qualifier in the name of the corresponding data set begins with the letter "I"). STYPE=J indicates that the concurrent copy was taken of the "J" instance of the table space (which means that the instance qualifier in the name of the corresponding data set begins with the letter "J" ).

To obtain a consistent offline backup copy outside of Db2:

  1. Start the Db2 objects that are being backed up for read-only access by issuing the following command: 
    -START DATABASE(database-name) SPACENAM(
tablespace-name) ACCESS(RO)
    Allowing read-only access is necessary to ensure that no updates to data occur during this procedure.
  2. Run QUIESCE with the WRITE(YES) option to quiesce all Db2 objects that are being backed up.
  3. Back up the Db2 data sets after the QUIESCE utility completes successfully.
  4. Issue the following command to allow transactions to access the data: 
    -START DATABASE(database-name) SPACENAM(tablespace-name)

If you use the CONCURRENT option:

  • You must supply either a COPYDDN DD name, a RECOVERYDDN DD name, or both. Note that the required JCL parameter specifications for the output data sets for the CONCURRENT option might differ from the JCL specifications required for sequential format data sets. For example, do not specify the BUFNO parameter for the output data sets when specifying the CONCURRENT option.
  • You can set the disposition to DISP=(MOD,CATLG,CATLG) if you specify the new data set for the image copy on a scratch volume (a specific volume serial number is not specified). You must set the disposition to DISP=(NEW,CATLG,CATLG) if you specify a specific volume serial number for the new image copy data set.
  • If you are restarting COPY, specify DISP=(MOD,CATLG,CATLG) or DISP=(NEW,CATLG,CATLG) for the COPYDDN and RECOVERYDDN data sets. The DFSMSdss DUMP command does not support appending to an existing data set. Therefore, the COPY utility converts any DISP=MOD data sets to DISP=OLD before invoking DFSMSdss.
  • If the SYSPRINT DD statement points to a data set, you must use a DSSPRINT DD statement.
  • If the page size in the table space matches the control interval for the associated data set, you can use either the SHRLEVEL CHANGE option or the SHRLEVEL REFERENCE option. If the page size does not match the control interval, you must use the SHRLEVEL REFERENCE option for table spaces with a 8-KB, 16-KB, or 32-KB page size.

Restrictions on using DFSMSdss concurrent copy

You cannot use a copy that is made with DFSMSdss concurrent copy with the PAGE or ERRORRANGE options of the RECOVER utility. If you specify PAGE or ERROR RANGE, RECOVER bypasses any concurrent copy records when searching the SYSIBM.SYSCOPY table for a recovery point.

You can use the CONCURRENT option with SHRLEVEL CHANGE on a table space if the page size in the table space matches the control interval for the associated data set.

Also, you cannot run the following Db2 stand-alone utilities on copies that are made by DFSMSdss concurrent copy:

  • DSN1COMP
  • DSN1COPY
  • DSN1PRNT

You cannot execute the CONCURRENT option from the DB2I Utilities panel or from the DSNU TSO CLIST command.

Requirements for using DFSMSdss concurrent copy

DFSMSdss concurrent copy is enabled by specific hardware. Contact IBM® or the vendor for your specific storage product to verify whether your controller or storage server supports the concurrent copy function.

Table space availability

If you specify COPY SHRLEVEL REFERENCE with the CONCURRENT option, and if you want to copy all of the data sets for a list of table spaces to the same dump data set, specify FILTERDDN in your COPY statement to improve table space availability. If you do not specify FILTERDDN, COPY might force DFSMSdss to process the list of table spaces sequentially, which might limit the availability of some of the table spaces that are being copied.