SPARC SuperCluster T4-4
 
SPARC SuperCluster T4-4 Half Rack
 
Oracle SuperCluster M6-32 Hardware
 
Solaris Operating System
 
Oracle SuperCluster M7 Hardware
 
Oracle SuperCluster M8 Hardware
 
Oracle SuperCluster Specific Software
 
Oracle SuperCluster T5-8 Half Rack
 
Oracle SuperCluster T5-8 Full Rack
 
SPARC SuperCluster T4-4 Full Rack
 

PLA-Support>Eng Systems>Exadata/ODA/SSC>SPARC SuperCluster>DB: SuperCluster_EST
 
_Old GCS Categories>ST>Server>Engineered Systems>SPARC SuperCluster>Performance
 
_Old GCS Categories>ST>Server>Engineered Systems>SPARC SuperCluster>Solaris 11 OS
 
_Old GCS Categories>ST>Server>Engineered Systems>SPARC SuperCluster>Solaris 10 OS
 

Applies to:

Symptoms

The use of DISM ( Dynamic Intimate Shared Memmory) on the SPARC  SuperCluster including the ASM instance can lead to several different issues ranging form excessive swap usage even when memory is available and expose bugs which can cause kernel panics and/or performance problems.  This led to not being able to take full advantage of AMM (Automatic Memory Management) on SuperCluster. Automatic Memory Management is now possible again with 12.1.0.1 and above database on Oracle Solaris 11.1 SRU 7.5 and above by leveraging the new Optimized Shared Memory (OSM) mechanism.

A dism_chk.sh script is available that can be run as UID 0 root user in any global zone which hosts databases or zones in which databases run.

An example of it's use assuming it is staged in /var/tmp on a GZ in which databases are in fact running....

o. One can also 'grep' for DISM processes running however in some cases one may be running even if there is no DISM in use...

Changes

In 12.1.0.1 and above we now support Optimized Shared Memory (OSM).

In 11.2  and 11.1 any database instance, including the ASM instance, that takes advantage of Automatic Memory Management (AMM) can trigger Dynamic Intimate Shared Memory (DISM) which is bad please see the checks in solution section below. Automatic Shared Memory Management (ASMM) is still supported and recommended.

Cause

 This is due to use of Dynamic Intimate Shared Memory (DISM) on Solaris, and is expected behaviour and not a defect, see the Oracle Database Administrator's Reference 11g Release 2 (11.2) for Linux and UNIX-Based Operating Systems, Appendix D 'Administering Oracle Database on Solaris' for more information.

The use of DISM requires that all or part of the SGA memory allocation be reserved in swap space as well as held in memory to allow the SGA to dynamically re-size .  DISM is activated automatically in Oracle when the value of the SGA_MAX_SIZE initialization parameter is larger than the sum of all SGA components combined or larger than value of SGA_TARGET. This enables Oracle Database to lock only the amount of physical memory that is currently being used in physical memory. In 11g, DISM is also activated by the setting of MEMORY_TARGET or MEMORY_MAX_TARGET in the same way as above.

Now in 12.1.0.1/ 11.1 SRU 7.5  and above you can use the Automatic Memory Management (AMM) parameters without harm thanks to Optimized Shared Memory (OSM).

Solution

12.1.0.1 and above enable Automatic Memory Management (AMM) via Optimized Shared Memory (OSM)

If you had previously removed Automatic Memory Management by resetting MEMORY_MAX_TARGET you can set it with alter system at the spfile level for all sids i.e :

Then Remove the SGA_MAX_SIZE and/or the SGA_TARGET parameters with a reset

 Then restart the database.

Below 12.1.0.1 - Prevent Dynamic Intimate Shared Memory (DISM)

To prevent this occurring you need to disable the use of DISM by Oracle on Solaris by either unsetting the SGA_MAX_SIZE / MEMORY_MAX_TARGET / MEMORY_TARGET parameters, or ensure SGA_MAX_SIZE is set to the same value as SGA_TARGET parameter or equal to the sum of all SGA components in the instance.

If you have the MEMORY_MAX_TARGET / MEMORY_TARGET parameters set then you should unset them with 

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References

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