3.4.6.4 Disabling Write Back Flash Cache on a Non-Rolling Basis for Software Versions Lower Than 11.2.3.3.1

You can enable Write Back Flash Cache on a non-rolling basis.

When changing the Flash Cache mode on a non-rolling basis, ensure the entire cluster is shut down, including the Oracle Clusterware stack and all the databases. The cell services must be shut down before changing the flashCacheMode attribute. The Flash Cache must be flushed and dropped before changing the attribute to writethrough. The Flash Cache flush operation can be performed prior to shutting down the entire cluster. After the flush operation begins, all caching to the Flash Cache stops.

1. Log in as the root user to the first database node to be disabled for write back Flash Cache.
2. Check the amount of dirty data in the Flash Cache using the following command:

   # dcli -g cell_group -l root cellcli -e "LIST METRICCURRENT ATTRIBUTES  \
           name,metricvalue WHERE name LIKE \'FC_BY_DIRTY.*\'"
   

3. Flush the Flash Cache using the following command:

   # dcli -g cell_group -l root cellcli -e ALTER FLASHCACHE ALL FLUSH
   

4. Check the status as the blocks are moved to disk using the following command. The count reduces to zero.

   # dcli -g cell_group -l root cellcli -e "LIST METRICCURRENT ATTRIBUTES name, \
          metricvalue WHERE NAME LIKE \'FC_BY_DIRTY.*\'"
   

5. Check the status of the flash disks using the following command:

   # dcli -g cell_group -l root cellcli -e LIST CELLDISK ATTRIBUTES name, flushstatus, flusherror | grep FD 
   

   The status shows completed when the flush is done.

6. Shut down the database and the entire cluster using the following commands:

   # cd Grid_home/bin
   # ./crsctl stop cluster -all
   

7. Drop the Flash Cache across all cells using the following command:

   # dcli -g cell_group -l root cellcli -e DROP FLASHCACHE
   

8. Shut down CELLSRV services using the following command:

   # dcli -g cell_group -l root cellcli -e ALTER CELL SHUTDOWN SERVICES CELLSRV
   

9. Set the flashCacheMode attribute to writethrough using the following command:

   # dcli -g cell_group -l root cellcli -e "ALTER CELL FLASHCACHEMODE=writethrough"
   

10. Restart cell services using the following command:

    # dcli -g cell_group -l root cellcli -e ALTER CELL STARTUP SERVICES CELLSRV
    

11. Re-create the Flash Cache using the following command:

    # dcli -g cell_group -l root cellcli -e CREATE FLASHCACHE ALL
    

12. Check the Flash Cache mode of the cells using the following command:

    # dcli -g cell_group -l root cellcli -e LIST CELL DETAIL | grep flashCacheMode
    

13. Restart the cluster and database using the following commands:

    # cd Grid_home/bin
    # ./crsctl start cluster -all