Wednesday, August 23, 2017

ODA X6-2 -- an important note about Migrating 11.2.0.4 databases to ODA X6

A few days ago, a follower of mine reported an issue using my forum.(http://ermanarslan.blogspot.com.tr/p/forum.html)

He was complaining about an error encountered while he was trying to restore a 11.2.0.4 database to ODA X6-2.
As ODA X6-2 supports both 11.2.0.4 and 12C databases, this issue seemed as not expected, in the first glance.

However; when I saw the error reported by my follower, I understood that there was a missing info about this restore thing.

Here, the follower said, they were trying to restore their 11.2.0.4 database to ODA X6, but they were getting "ORA-15204: database version 11.2.0.4.0 is incompatible with diskgroup DATA"

The whole error stack was as follows;

ORA-17502: ksfdcre:3 Failed to create file +DATA/PROD/datafile/a_txn_data04.dbf
ORA-15001: diskgroup "DATA" does not exist or is not mounted
ORA-15204: database version 11.2.0.4.0 is incompatible with diskgroup DATA

Well.. When I see the stack, I saw that , the restore operation was trying to be done directly on ASM.
As Grid deployed with ODA X6 is 12C and as the database compatabilities of the ASM diskgroups that come with the ODA deployment, are 12C; the error, that the follower was getting, was actually normal and expected.!

"That is, if you want to restore a 11.2.0.4 database to ODA, you don't use ASM diskgroups directly..
So you use ACFS filesystem rather than ASM diskgroups.."
ODA's Appliance Manager does it with the same way.

Here is what I suggested to my follower:
  • Use ACFS in ODA X6-2. 
  • Create a dummy 11.2.0.4 database from Appliance Manager .. This action will create an ACFS filesystem for you. 
  • Delete that dummy database using standard approaches and use the created ACFS filesystem for your restore. 
Why did you want him to create a dummy database using Appliance Manager?
Because , I want his restored database to be seen in the Appliance Manager.. I wanted him to have a clean environment :)

Well. This is the tip of the day, but it is important right?
Anyways, use ACFS and know the following;

  • ACFS uses ASM in the backend. It is an filesystem built on top of ASM. 
  • ACFS is much more useful than ASM. 
  • For instance; ASM has a limit of 1 million files per Diskgroup. ACFS, on the other hand; supports 2^40 (1 trillion) files in a file system. 
  • ACFS has also the snapshot ability. 
  • Oracle uses ACFS in its new Enginereed Systems, but still it requires ASM. ACFS uses it. So nothing is useless in engineered systems :) 

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