- David Sciaraffa, Software Development Manager – IBM Db2 Availability
System failures happen. Modern enterprise IT stacks are complex feats of software and hardware engineering, encompassing billions of physical transistors and billions of lines of logical code comprising an almost infinite number computational permutations. These stacks run in data centers with physical attributes such as electrical utility and temperature conditions. Lest we forget the most vulnerable component of the IT stack - human error. Thus, system failures happen.
While system failures seldom happen, most customers expect crash recovery to complete quickly. Since a database administrator can never fully prevent poorly tuned applications, a common customer request is for quicker accessibility to the database after a system failure, during crash recovery.
Our development team decided upon a solution which promised increased availability, without risking the distinguished resilience that Db2 has achieved over the decades.
The DB2_ONLINERECOVERY feature was rolled out in Db2 Version 184.108.40.206.
The feature allows for the database to become connectable once the forward phase of crash recovery has completed, while the backward phase of crash recovery is progressing. Tables which contain data changes that need to be undone during the backward phase of crash recovery will not be accessible to queries until the last of their data changes is undone. All other tables are fully accessible to queries throughout the backward phase of crash recovery.
To read further about this new cool feature, please see David's blog post.