Document Type | Technical Information
Category | Backup/Recovery
Applicable Product Versions | 6FS07, 6FS07PS, 7FS01, 7FS02, 7FS02PS
Document Number | TBATI009
Overview
This document explains the optimization of recovery performance and maintenance of query consistency focusing on the Standby Recovery methods MMR (Multi Memory Recovery) and TMMR (TSN Memory Media Recovery).
Methods
MMR (Multi Memory Recovery)
- Performance improvement: IO for recovery target blocks operates as Multi Block Read, and recovery performance is enhanced using the AIO method.
- Recovery target blocks are loaded into cache for processing.
- Advantages of MMR: Supports Multi Block Read/Write
TMMR (TSN Memory Media Recovery)
- During recovery in the existing Standby, Redo Records are applied using MMR. To utilize MMRโs advantages such as MBR/MBW functions, recovery is performed in DBA order rather than TSN order.
- However, recovering in DBA order causes issues when a SELECT QUERY executes while the space meta block is applied first and the referenced Data block has not yet been applied.
- Therefore, to resolve this issue and maintain MMRโs advantage of MBR, TMMR was developed to perform recovery of Redo records in TSN order to guarantee SELECT QUERY consistency.
- Since recovery on a per Redo record basis causes random IO, all blocks to be modified are preloaded into cache and used on disk after recovery is completed.
- TMMR process:
- All recovery target blocks are loaded into cache. (MBR)
- Set ex pin lock to prevent cached blocks from being evicted.
- Apply redo record recovery in TSN order, setting bucket lock on the blocks being modified. (If a SELECT query arrives while bucket lock is held, it waits until the lock is released)
- After applying all redo records for recovery, release the cache.
Caution
When in READ ONLY mode