Monitoring FUSION-WRITE RAC 12c

In RAC, blocks are written from cache to disk when checkpoint occurs, aging and when user request new data i.e cache replacement. Oracle send's message to notify other instances that oracle will perform FUSION-WRITE to move datablock from disk :)

Fusion - Writes can be monitored with following sql

select
a.inst_id "Instance",
A.value/B.value "cache fusion writes Ratio"
FROM
GV$SYSSTAT A,
GV$SYSSTAT B
WHERE
a.name='DBWR fusion writes'
AND b.name='physical writes'
AND b.inst_id=a.inst_id
ORDER BY
A.INST_ID;

If the ratio is larger we can notify more blocks are copied with previous changes between instances and we have to work on Tuning cache sizes and Checkpoints

--Nikhil Tatineni--
--12C RAC ---

Knowledge on RAC
12c: RAC Environment
http://oracle-in-memory.blogspot.com/2016/02/rac-environment.html
12c: RAC Blocked Listener
http://oracle-in-memory.blogspot.com/2016/02/12c-rac-blocked-listener.html
12c: RAC Health Checks
http://oracle-in-memory.blogspot.com/2016/02/rac-health-checks-12c.html
RAC Diagwait
http://oracle-in-memory.blogspot.com/2016/02/rac-diagwait.html
12c: Oracle Local Registry(OLR)
http://oracle-in-memory.blogspot.com/2016/02/12c-olr-oracle-local-registry.html
12c: Applying Database Rolling Patch on RAC Cluster
http://oracle-in-memory.blogspot.com/2016/02/applying-database-rolling-patch.html
12c: Resize Online redolog files 
http://oracle-in-memory.blogspot.com/2016/02/resize-online-redologs-files-12c-rac.html
RAC: Creating service using srvctl on pdb 
http://oracle-in-memory.blogspot.com/2016/02/rac-creating-service-on-pdb.html
12c: Mirror copy of OCR onto different asm diskgroup
http://oracle-in-memory.blogspot.com/2016/02/oracle-rac-mirror-copy-of-ocr-onto.html 
12c: Pin Nodes On Cluster
http://oracle-in-memory.blogspot.com/2016/02/12c-pin-nodes-on-cluster.html
12c: RAC Modify Default scan port Number
http://oracle-in-memory.blogspot.com/2016/02/12c-rac-modify-default-scan-port-number.html
12c: Mutiplex Voting Files on Oracle RAC 12C
http://oracle-in-memory.blogspot.com/2016/02/multiplex-voting-files-on-oracle-rac-12c.html
12c:converting database from No Archivelog mode to Archivelog Mode
http://oracle-in-memory.blogspot.com/2016/03/converting-12c-rac-database-to.html
12c: Creating New Virtual IP to manager HA 
http://oracle-in-memory.blogspot.com/2016/03/oracle-goldengate-creating-virtual-ip.html
CRS-4535 12C RAC Cluster
http://oracle-in-memory.blogspot.com/2016/02/12c-rac-crs-4535.html
CRS-8503 12C RAC Cluster
http://oracle-in-memory.blogspot.com/2016/03/crs-8503.html