Planning for backup and recovery
To guard against system failures that affect your CSD, take a backup of the CSD at regular intervals. Then, if the CSD is corrupted for any reason, you can restore it to its state at the last backup.
About this task
To keep the backup of the CSD as up-to-date as possible, make an image copy of your CSD before each period of update activity, either by an RDO transaction or DFHCSDUP.
Alternatively, because the CSD is open for update whenever RDO work is taking place, it is a good candidate for eligibility for BWO. If the CSD is specified as eligible for BWO, and the data set is corrupted, you can restore a BWO image of the CSD using DFSMSdss, then run forward recovery to the point of corruption using a forward recovery utility.
For a CSD opened in RLS mode, the recovery attributes must be defined in the ICF catalog entry for the CSD, and CICS® uses the forward recovery log's log stream name (LSN) from the ICF catalog.
For a CSD opened in non-RLS mode, the recovery attributes can be defined in the ICF catalog entry for the CSD, or on the CSD system initialization parameters. The forward recovery log stream name (LSN) is retrieved from either CSDFRLOG or the ICF catalog. If LOG is defined in the catalog, the forward recovery log stream specified in the catalog is used. If LOG is not defined, the CSDFRLOG journal ID is used to determine the log stream name. If the NONRLSRECOV system initialization parameter is set to FILEDEF, the CSDFRLOG journal ID is always used to determine the log stream name. Any recovery attributes specified on the ICF catalog are ignored.
For a CSD opened
in non-RLS mode, you can use the system initialization parameter CSDBKUP=DYNAMIC|STATIC
to indicate whether the CSD is eligible for BWO. Specify CSDBKUP=DYNAMIC
for BWO support, or STATIC (the default) for a normal
quiesced
backup. If you specify BWO support for the CSD you must also define
it as forward recoverable. For more information about BWO, see Defining backup while open (BWO) for VSAM files.
For a CSD opened in RLS mode, you must specify all recovery attributes, which includes backup, in the ICF catalog. BWO backup eligibility is specified using BWO(TYPECICS).
If you specify forward recovery for the CSD, changes (after images) made by CICS to the CSD are logged in the forward recovery log stream. Using the latest backup, and the after images from forward recovery log stream, you can recover all the changes made by running a recovery program, such as the CICS VSAM forward recovery utility. After performing forward recovery, you must reenter any CEDA transactions that were running at the time of failure, as these are effectively backed out by the forward recovery process. You can find details of these in the CSDL transient data destination, which is the log for copies of all CEDA commands. See Logging RDO commands for more information.
Recoverability, forward recovery log stream names, and BWO eligibility can be defined optionally in the ICF catalog for a non-RLS accessed CSD, but must be defined the ICF catalog if the CSD is accessed in RLS mode.
The CSDBKUP, CSDRECOV, and CSDFRLOG system initialization parameters interact according to how they are specified. Table 1 and Table 2 summarize their effects when the SIT is assembled and during CICS override processing, respectively.
| CSDRECOV | CSDFRLOG | CSDBKUP | Result |
|---|---|---|---|
| ALL | FRLOG from 01 through 99. | Either DYNAMIC or STATIC | OK |
| ALL | NO | Either DYNAMIC or STATIC | SIT assembly fails with MNOTE stating that CSDRECOV=ALL implies that the CSDFRLOG option must be specified. |
| BACKOUTONLY or NONE | FRLOG from 01 through 99. | DYNAMIC | SIT assembly fails with assembler MNOTES stating that CSDBKUP=DYNAMIC requires CSDRECOV=ALL and that CSDFRLOG requires CSDRECOV=ALL. |
| BACKOUTONLY or NONE | NO | DYNAMIC | SIT assembly fails with an assembler MNOTE stating that CSDBKUP=DYNAMIC requires CSDRECOV=ALL. |
| BACKOUTONLY or NONE | NO | STATIC | OK |
| BACKOUTONLY or NONE | FRLOG from 01 through 99. | STATIC | SIT assembly warning MNOTE stating that CSDFRLOG is ignored unless CSDRECOV=ALL. |
- When CSDBKUP=DYNAMIC, the CSD is eligible for BWO.
- Backup and recovery attributes must be specified in the ICF catalog for a CSD opened in RLS mode (CSDRLS=YES).
- Backup and recovery attributes can optionally be specified in the ICF catalog for a CSD opened in non-RLS mode (CSDRLS=NO), but you must still have a consistent set of parameters as defined in the table above.
| CSDRECOV | CSDFRLOG | CSDBKUP (see Notes) | Result |
|---|---|---|---|
| ALL | FRLOG from 01 through 99. | Either DYNAMIC or STATIC. | OK |
| ALL | NO | Either DYNAMIC or STATIC. | Message DFHPA1944 is issued stating that CSDRECOV=ALL cannot be specified without a CSDFRLOG if CSDRLS=NO. CICS initialization is terminated. |
| BACKOUTONLY or NONE | FRLOG from 01 through 99. | DYNAMIC | Processing continues and messages DFHPA1929, stating that CSDBKUP has defaulted to STATIC, and DFHPA1930, stating that CSDFRLOG has been ignored, are issued. |
| BACKOUTONLY or NONE | NO | DYNAMIC | Processing continues and message DFHPA1929 is issued, stating that CSDBKUP has defaulted to STATIC. |
| BACKOUTONLY or NONE | NO | STATIC | OK |
| BACKOUTONLY or NONE | FRLOG from 01 through 99. | STATIC | Processing continues and message DFHPA1930 stating that CSDFRLOG has been ignored is issued. |
- When CSDBKUP=DYNAMIC, the CSD is eligible for BWO.
- Backup and recovery attributes must be specified in the ICF catalog for a CSD opened in RLS mode (CSDRLS=YES).
- Backup and recovery attributes can optionally be specified in the ICF catalog for a CSD opened in non-RLS mode (CSDRLS=NO), but you must still have a consistent set of parameters as defined in the table above.
Write and test procedures for backing up and recovering your CSD before beginning to operate a production CICS region.
Forward recovery of the CSD is not possible if CSD updates are made outside CICS. To enable recovery of the updates made outside CICS, you need to use an image copy. If you update the CSD from outside CICS, do not use CEDA to update the CSD until an image copy has been made.