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TSC (Tiber Standby Cluster) Recovery: Two Methods

Document Type | Technical Information

Category | Administration

Applicable Product Versions | 6FS06, 6FS07, 6FS07PS, 7FS01, 7FS02, 7FS02PS

Document Number | TADTI041

 

Overview

In the TSC (Tiber Standby Cluster) environment, the recovery method is handled in two ways depending on the operating mode.
This explains the recovery methods MMR and TMMR, which are applied respectively in recovery mode and read-only mode.
 
 

Methods

The TSC (Tiber Standby Cluster) recovery method differs as follows depending on whether it is in recovery mode or read-only mode.
  • Recovery Mode: MMR (Multi-Master Replication) method applied
  • Read-Only Mode: TMMR (TSN-based Multi-Master Replication) method applied
 

1. MMR (Multi-Master Replication)

  • MMR is used in TSC to apply redo records.
  • MMR performs recovery of redo records in DBA order rather than TSN order to support MBR (Multiple Block Read) and MBW (Multiple Block Write) functions.
  • Because it proceeds in DBA order, space meta blocks are applied first, and if a select query arrives while data blocks that have not yet been applied are pointed to, problems may occur.
  • When the Standby DB is in recovery mode, it is applied through MMR.
Note
space meta block : Refers to metadata blocks such as Tablespace (logical data storage unit), Segment (actual storage area of an object), Extent (a contiguous block set forming a segment), Block (minimum unit of disk I/O), and space management. 
 

2. TMMR (TSN Multi-Master Replication)

  • To ensure select query consistency, redo records are recovered in TSN order.
  • All blocks to be recovered using MMR are loaded into cache. (At this time, an exclusive pin lock is applied to prevent cache out.)
  • Redo record recovery proceeds in TSN order, applying a bucket lock to the blocks being modified. Because bucket locks are held, if a select query arrives during recovery, it waits until the lock is released.
  • After all redo record recovery is processed, the cache is released.
  • When the Standby DB is in read-only mode, it is applied through TMMR.
     
     
 
 

 

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