Backout Integrity report
Use the Backout Integrity report to determine the impact of performing an UNDO or a REDO operation, and to weigh the benefits of applying UNDO SQL versus REDO SQL.
Additionally, the report supplies information about the set of objects that are affected by the changes, and the volume of information affected. The report presents only the data defined by your time frame and filter, and only data associated with committed transactions.
The Backout Integrity report is a default output for the following choices under the Actions category on the Main Menu:
- Analyze Problem Transactions
- Create UNDO SQL
- Create REDO SQL
To request a Backout Integrity report, from any task dialog (any option from 0 through 7 under the Actions category on the Main Menu), select the Define Report and File Outputs option, and then, on the Output Options panel, select Backout Integrity.
Be aware of the following points as you define a Backout Integrity report:
- Log Master can produce the Backout Integrity report in two formats: Detail (including field data and all URID information), and Summary (omitting field data and some URID information).
To generate a Backout Integrity report, Log Master scans the Db2 log up to the current time, even when you do not specify the end point of your time frame as CURRENT. Log Master takes this action because the log records that you select may be affected by subsequent transactions that occur after your time frame.
Log Master defines the current time as the last relative byte address (RBA) or log record sequence number (LRSN) that Db2 has written to the log when the Log Master job begins executing.
- In general, Log Master uses more resources to generate a Backout Integrity report than it does to generate other reports. Log Master can use more CPU and I/O time time, and scan more log to generate a Backout Integrity report than you might anticipate based on your filter and time frame.
- Log Master cannot produce either version of a Backout Integrity report when the input source of your log scan is individual Db2 log files (INPUT DB2LOG).
- The Backout Integrity report tracks subsequent changes that affect rows selected by your filter and time frame. Log Master tracks these changes using the record IDs (RIDs) and unique key values of the original selected rows. If the original row has a unique key, Log Master can track changes even when Db2 moves the row because of overflow, or when the row is deleted and then re-inserted with the same key value.
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