Testing procedure and verifying a recovery

Recovering a data entry database (DEDB) area after an IMS system failure by using Fast Path Recovery Utility is functionally equivalent to recovering the area by using the IMS Recovery utility (DFSURDB0).

For information about the available testing utilities, see Testing-utilities-TSSAFR7-TSSAFR8-TSSAFR9.

Testing procedure

After an IMS system fails (or has been modified down), perform the following steps:

1. Execute the Fast Path Recovery Utility recovery as described in DEDB-Recovery-utility-TSSAFR2 but do not restart the IMS system.
2. Take an image copy of selected area data sets.
3. Run the BMC Fast Path Analyzer/EP product against selected areas.For more information, seeFast Path Offline Suite documentation.
4. Define new VSAM clusters for the selected areas (with different data set names), and perform a complete forward recovery by using the previous image copy and all required log data sets.
5. Take an image copy of the recovered area data sets.
6. Run Fast Path Analyzer/EP product against the recovered areas.
7. Compare Fast Path Analyzer/EP reports from the Fast Path Recovery Utility recovered area to those from the DFSURDB0 recovered area.The reports, including all statistics, will be identical.
8. Compare the image copy of the Fast Path Recovery Utility recovered area to the image copy of the DFSURDB0 recovered area (use IEBCOMPR or an equivalent comparison program).Except for the physical differences outlined previously, the copies will be identical.
9. To further verify the contents of the sequential dependent part of an area, perform the following steps:
   1. Run the DEDB Sequential Dependent Scan utility against the Fast Path Recovery Utility recovered area, and save the output data set.
   2. Delete the Fast Path Recovery Utility recovered area, and rename the DFSURDB0 recovered area to the correct data set name.
   3. Run the IBM DEDB Sequential Dependent Scan utility against the renamed area.The number of sequential dependents written out, as well as the output file contents, will be identical.
10. To further verify the logical content of the Fast Path Recovery Utility recovered area, run an unload of the Fast Path Recovery Utility recovered area against an unload of the DFSURDB0 recovered area.The number of segments unloaded from each area data set will be identical.

Verifying a recovery

One method of verifying a Fast Path Recovery Utility recovery is to compare the image copy of an area recovered by Fast Path Recovery Utility with the image copy of an area recovered by the DFSURDB0 recovery utility.

The following exceptions to an exact physical comparison exist:

• The image copy header records will differ (the image copy date/time stamp will not be the same).
• The DEDB master area control block control interval (DMAC CI) might contain minor differences after offset +5C. These fields will be reset by IMS at the next area data set (ADS) open.
• The current sequential dependent buffer, and any sequential dependent buffers waiting completion of an output thread at the time of the selected Checkpoint-ID, will be logically the same (from the perspective of the DEDB Sequential Dependent Scan utility) but can be physically different.

These physical differences are caused by the following processing differences:

• During recovery, DFSURDB0 reads the CI (which will contain old sequential dependent part (SDEP) segments if the SDEP part has wrapped) and applies the 5950 records for each SDEP segment that was inserted into the CI. IMS always logs the segment data plus one byte of binary zeros (the extra byte of binary zeros will terminate the Scan utility).
• During a Fast Path Recovery Utility recovery, a DEDB update record that contains the entire CI (the image of the buffer at the selected checkpoint) is applied plus any SDEP inserts after the checkpoint. Because IMS preformats a new SDEP buffer to binary zeros, the SDEP data from the previous cycle is not present.

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