What data is unavailable?
One difference between the non-data-sharing and the data sharing implementation of postponed backout is the degree of data unavailability.
In non-data-sharing, Db2 places any page set or partition that has pending backout work into a restrictive status called restart pending, which blocks access to data at the page set or partition level.
In data sharing, no restrictive status is set. Access to data with
pending backout work is blocked by transaction locks that persist
through restart. The following retained locks persist through restart
when postponed backout processing is active:
- Retained transaction locks held on page sets or partitions for which backout work has not been completed
- Retained transaction locks held on tables, pages, rows, or LOBs of those table spaces or partitions
The retained transaction locks on any particular page set or partition are freed when all URs using that page set or partition have completed their backout processing. Until that happens, the page set or partition is placed in an advisory status called advisory restart-pending (AREST).