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  Oracle Database Tips by Donald Burleson

Oracle10g Grid Computing with RAC
Chapter 7 - Cache Fusion and Inter Instance Coordination

Recovery Process - Re-mastering Resources

Scenario 1:

Neither the recovering instance (A) nor the open instance (B) has a lock element (or it may be in NL0 mode). This indicates that the failed instance had XL0. Therefore, SMON acquires a lock in XL0 mode, reads the block from disk, and applies redo changes. Therefore, the block is kept in the recovery set. (Later, DBWR writes the recovery buffer out when recovery is completed.)


Figure 7.8 Lock Re-Mastering - (Scenario-1)

Scenario 2:

Instance (B) has the block buffer in either XL0 mode (or SL0), but the recovering instance (A) does not have anything. Since instance (B) is holding the lock in exclusive local mode, it is more current than the redo stream. Therefore, no recovery is needed. There is also no need to write this block to disk.


Figure 7.9 Lock Remastering - (Scenario-2)

The above text is an excerpt from:

Oracle 10g Grid & Real Application Clusters
Oracle 10g Grid Computing with RAC
ISBN 0-9744355-4-6

by Mike Ault, Madhu Tumma


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