TurboIMAGE/XL Database Management System Reference Manual MPE/iX V6.5 (30391-90011)
Appendix G 661
Recovery and Logging Quick Reference
Recovery Quick Reference
• When the roll-forward process finishes, the RESTART option in user logging can be used
or a new logging cycle can be started. Remember to purge the log files before starting
the new logging cycle.
• May not recover all transactions. If using DBEND mode 2, transactions will be flushed to
the log file at DBEND time; therefore, transactions will not be lost.
• You should consider how often to store the database. The more frequent the backup, the
smaller the log files will be, thus cutting the time required for recovery.
Roll-Forward Flag Settings
The recommended settings for TurboIMAGE/XL flags used for roll-forward recovery are
shown in the following table. Note that the flags change depending on whether you are
storing a database, running in production, or initiating a database recovery.
Roll-Back Recovery
• Provides rapid recovery of database integrity following a soft system crash and restores
the database to a consistent state, physically and logically, by backing out any
incomplete transactions.
• Requires logging. Storing the database is recommended but not required. (Logging is
automatically enabled when roll-back is enabled.)
• If logging to disk, requires that the database and the user log file be on the same volume
set.
• If logging to tape, requires that the database be on the system volume set.
• Is initiated with the >ROLLBACK command of DBRECOV.
• When disabled, logging must be manually disabled using DBUTIL.
• Requires all multiple-intrinsic database transactions to execute independently, using
logical transaction locking.
• Uses the time stamp during recovery to verify the correct log file for each database
being recovered. The time stamp is updated when the database is first opened and is
logged to the log file and the root file.
Table G-1. Roll-Forward Flag Settings
Flags True-Online Backup DBSTORE Production DBRECOV
Access Disabled/Enabled Disabled Enabled Disabled
AUTODEFER Disabled/Enabled Disabled Disabled/Enabled Disabled
Dumping Disabled Disabled Disabled Disabled
ILR Disabled Disabled Disabled Disabled
Logging Enabled Enabled Enabled Enabled
Recovery Disabled/Enabled Enabled Disabled Enabled
Roll-back Disabled Disabled Disabled Disabled