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Oracle 12c Flex ASM

Oracle’s Automatic Storage Management (ASM) serves many purposes as part of Oracle Grid Infrastructure RAC/non-RAC. It is somewhat similar to Veritas volume manager but provides many features than a simple volume manager and it is free of cost.Since 11g , ASM has been a stable product. Many RAC installations moved from vendor specific shared storage to ASM due to it is simplicity and this is the default storage option supported by Oracle for RAC implementation unless you do upgrades.

With Oracle 12c, ASM got many new features to make it more robust and highly available. One of the very interesting additions is called “Flex ASM”. With this option you can run ASM in flex mode. Flex ASM eliminates the need for running ASM instances on each RAC node. Number of ASM instances is controlled through “cardinality”. It is recommended to have cardinality value of 3. For example if you have 12 nodes cluster, you can just run 3 ASM instances on 3 nodes. All 12c databases running on that cluster will connect to these 3 ASM . In the event of one ASM crashes on any of the 3 nodes, GI will start ASM on another node. 12c database on the node where ASM failed will be up & running by connecting to other ASM and it will be transparent to applications. Automatic connection transfer to surviving ASM node is 12c database specific feature and it is not available on 11g database kernel. If you want to run in a mixed mode 12c and 11g databases, it is a good idea to have cardinality to “All”. That way 12c databases can take advantage of new remote ASM connection failover.

Flex ASM comes with following additional features: ( I am not sure if these features are available with 12c standard mode ASM also. Oracle product manager thinks it is but oracle documentation contradicts it)

  • Number disk group limitation now 511 ( previously 63)Changing disk names allowedOptional dedicated ASM network
  • Many improved disk failure and data corruption handling
  •  Replace ASM disk instead of adding and removing disk. This feature saves significant rebalance activity
  • On demand data scrubbing for detecting corruption
  •  Even read of data from Primary and secondary mirror copies if you have ASM mirroring which possibly improves IO performance
  • Offload extent relocation to Exadata storage cells
  • Automatic Version validation for newly joining ASM instance.

Oracle DBA related google/yahoo searches – Avoiding hits from same websites (like dba-oracle)

As an oracle DBA when you google up information on the web I always get top hits from dba-oracle and other websites hosted by Mr.Burleson. I am not questioning his expertise but here are the problems :

1) His websites most of the time provides just piece meal information in a very tricky way so that you can buy his books or services etc. He always reminds of used car sales man.

2) The top hits  from these same web sites masks the results from great independent bloggers.

This is what you need to need . Add  minus sign at the end of your key words. Example:

Following search from google:

oracle tuning tips  -dba-oracle 

will produce



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