To proactively avoid/prevent the issues associated with DISM, itis highly recommended to disable the use of DISM on ALL instanceshaving an SGA larger than 4GB by either unsetting the SGA_MAX_SIZE/ MEMORY_MAX_TARGET / MEMORY_TARGET parameters, or ensureSGA_MAX_SIZE is set to the same value as SGA_TARGET parameter orequal to the sum of all sga components in theinstance. For a detailed description of DISMplease see Document 1472108.1.
Oracle Database - Enterprise Edition - Version 10.2.0.5 to 12.1.0.1[Release 10.2 to 12.1] Oracle Solaris on x86-64 (64-bit) Oracle Solaris on SPARC (64-bit)
Symptoms
The use of DISM on Solaris systems (SPARC and x86-64) outside ofthe ASM instance can lead to several different issues ranging fromexcessive swap usage even when memory is available to kernel panicsto performance problems. It has been determined by engineering thatthe ASM instance is typically such a small memory footprint that itshould not cause an issue.
From a Database and/or Clusterware perspective the Symptomsinclude:
Overall Poor Performance including login problems
Processing Delays Resulting in IPC errors
Instance Evictions
Node Evictions
From a system perspective the Symptoms include:
High System Time (often exceeding 50%)
GUDs will show numerous threads in the ipc_get system call
Excessive swap usage
Kernel Panics
Changes
N/A
Cause
This is due to use of Dynamic Intimate Shared Memory (DISM) onSolaris, see the Oracle Database Administrator's Reference 11gRelease 2 (11.2) for Linux and UNIX-Based Operating Systems,Appendix D 'Administering Oracle Database on Solaris' for moreinformation.
The use of DISM requires that all or part of the SGA memoryallocation be reserved in swap space as well as held in memory toallow the SGA to dynamically re-size . DISM isactivated automatically in Oracle when the value of theSGA_MAX_SIZE initialization parameter is larger than the sum of allSGA components combined or larger than value of SGA_TARGET. Thisenables Oracle Database to lock only the amount of physical memorythat is currently being used in physical memory. In 11g, DISM isalso activated by the setting of MEMORY_TARGET or MEMORY_MAX_TARGETin the same way as above.
Solution
To determine if DISM is is in use the PMAP utility may beused:
To proactively avoid/prevent the issues associated with DISM, itis highly recommended to disable the use of DISM on ALL instanceshaving an SGA larger than 4GB by either unsetting the SGA_MAX_SIZE/ MEMORY_MAX_TARGET / MEMORY_TARGET parameters, or ensureSGA_MAX_SIZE is set to the same value as SGA_TARGET parameter orequal to the sum of all sga components in theinstance. For a detailed description of DISMplease see Document 1472108.1.
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