Oracle Tips by Burleson

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

Recovery Process – Re-mastering Resources

Scenario 3:

Instance (B) has the block buffer in either XG# mode or SG# mode (both global), but the recovering instance (A) does not have anything. Here, the resource is in global role. Therefore, SMON initiates the write of the current block on instance (B). No recovery is needed because a current copy of the block exists in instance (B). The entry is removed from the recovery set. Write completion will release the recovery buffer and instance A acquires NG1.

Figure 7.10 Lock Remastering – (Scenario-3)

Scenario 4:

The recovering instance (A) does not have anything and instance (B) has NG1 mode, which indicates the failed instance had the more current block (maybe something like XG0). Therefore, instance (A) gets a consistent-read image block based on SCN from instance B, and acquires XG0 mode. It keeps the block in the recovery list.

Figure 7.11 Lock Re-Mastering – (Scenario-4)