gc cr block 2-way

gc cr block 2-way (read/read or write/read with 2 nodes)

Definition

Case-1: WRITE/READ


- Requesting instance request any CR data block for select from Master.
- If master is the holder of that data block and also has already modified that block.
- Then master will prepare CR copy of that data block (using undo).
- Finally Master instance serve CR block to the requesting instance.
- Meanwhile requesting instace will wait in "gc cr block 2-way"



Case-2: READ/READ

- Requesting instance request any CR data block for select from Master.
- If master is the holder of that data block and has not already modified that block.
- Master instance serve CR block to the requesting instance immediatly.
- Meanwhile requesting instace will wait in "gc cr block 2-way"

Reason

- In both the cases you will encounter this wait event in "TOP-5" section of AWR Report.
- Plan of action would be similer like "gc current block 2-way"