Exadata flash cache enabled for write back stefans blog. Installations,upgrades on all flavors of unix linux,solaris,hpaix. Exadata smart flash cache overview write through and. The exadata smart flash cache is a cache on the cell storage server for storing redodata until this data can be safely written to disk. Smart flash cache in oracle exadata 2 it tutorials. With the announcement exadata x3, oracle has introduced a new feature called flashcache writeback to allow writes to cell flash cache aka exadata smart flashcache in writeback mode. The exadata storage server comes with a substantial amount of flash storage. Oracle ebusiness suite r12 upgrades, patching,cloning on all environments aws upgrade and implementation expert.
Why writethrough is still the default flash cache mode on. Here are the concepts of exadata patching to make exadata. Because the system was used in a 247 environment we had to implement the change in a rolling upgrade fashion. Earlier with writethrough mode, writes were not written to flashcache, instead they were written directly to cell disks. In the case of high redundancy this means a write of, say, 8kb will result in 3 copies of the 8kb block to be cached in exadata writeback cache in the flash cards of the cells that have the hdd backingstore for the blocks. Write caching eliminates disk bottlenecks in large scale oltp and batch workloads.
Before jumping into the procedure itself, lets remind that the storage cells must run 11. Smart flash cache logging redo logs are written to the disk and flash memory at th. Exadata software used to decide whether to cache these writes back into flashcache or not. The exadata smart flash cache is a cache on the cell storage server for storing redo data until this data is safely written to disk. Yes, this is wellknown and the process has been described in exadata writeback flash cache faq doc id 1500257. The flash write capacity of a single full rack exadata database machine x42 exceeds 1,960,000. I had to enable the wbfc many times before and every time id restart the cell services, as note suggests. This was the point where we would like to test what happens when we change the flash cache mode from write through to write back. Database architect,oracle rac dba,apps dba,sap,mysql,mongodb,postgressql administration with 12yrs of experience mongodb replica sets,sharding. Here are the concepts of exadata patching to make exadata dba life easy patching database is a common task for a remote dba, but when we talk about exadata patching it. In a recent tuning activity it was necessary to change the exadata smart flash cache from writethrough to writeback. From one db node using dcli check the currest status of the. Smart flash cache in oracle exadata 3 it tutorials.