Today, this is all much simpler through Fast-Start Fault Recovery. The Oracle database
automatically bounds recovery time at startup using self-tuned checkpoint
processing, first introduced in Oracle Database 10g.
Rollback improvements
The rollforward phase re-creates uncommitted transactions and their associated
rollback information. These in-flight transactions must be rolled back to return to a
consistent state.
In Oracle releases prior to Version 7.3, the database wasn??™t available until all uncommitted
transactions rolled back. Although a DBA could control the checkpoint frequency
and therefore control the time required for the rollforward phase of instance
recovery, the number of uncommitted transactions at the time of the crash varied tremendously
so the time needed for rollback could not really be accurately controlled
or predicted. In a busy OLTP system, there are typically a fair number of in-flight
transactions requiring rollback after a crash. This situation led to variable and unpredictable
times for crash recovery.
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