TRANSDB requires backup protection since it nearly always contains unfinished transactions. If TRANSDB is lost before the Mimer SQL system is restarted, the database will be left in a logically inconsistent state.
Possible effects of losing TRANSDB before the database server is restarted are described in the following scenarios:
- If TRANSDB is lost, some of the databank updates that apply to the most recently committed transactions may have been made while others remain unfinished.
The only safe operation to do to avoid a logically inconsistent database is to bring up the most recent backup copy and restore from LOGDB. In this case, the only loss is those transactions that were not completely written to LOGDB.
- If both TRANSDB and LOGDB are lost, the restoration, as described in the previous bullet, cannot be accomplished.
In the case where a restore is not possible, the best solution is to repair the inconsistency immediately after restarting the database server. This is done by using a tool such as BSQL for manual verification and update of data. This is usually possible if the user who initiated the interrupted transaction can be identified and contacted. (Many applications maintain a parallel audit log file for tracking purposes which can be used as a basis for repair work).
An alternative solution if both LOGDB and TRANSDB are lost, is to start over from the most recent backup of your databanks and reprocess all transactions since that time. This may be a costly operation.
Keeping TRANSDB and LOGDB on separate disks under separate disk controllers will minimize the risk that both databanks are lost at the same time.
A TRANSDB shadow is another possible security enhancement, see Shadowing Functionality.
Note: The TRANSDB system databank must never be deliberately deleted, because uncompleted transactions nearly always remain saved in the databank even if the database server is currently stopped.
If a TRANSDB file containing uncompleted transactions is deleted, inconsistency will occur because the information required to complete those transactions when the database server is re-started will have been lost.
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