Oracle 9i now claims - found in doc 151222.1 [Solaris limitation: Keep in mind that on most Unix platforms, Oracle9i will allocate sufficient shared memory segment(s) to have a total sized at, or just above the size specified by SGA_MAX_SIZE when the instance is started. The default behavior on Solaris platforms is to lock this/these shared memory segment(s) into physical memory by forcing the use of ISM (Intimate Shared Memory). This is the default behavior of Oracle and is due to the operating system limitation in the shared memory management area. It is not recommended to disable this behavior as a serious performance penalty will be incured. In Solaris 8, thanks to DISM support (Dynamic Intimate Shared Memory), it is possible to avoid the above limitation and allocate the shared memory segment such that only the active granules in the SGA are located in physical memory. All unused granules will be stored in swap until needed].

I attempted to enable DISM and followed the instructions found in that document but cannot get anywhere. I consulted Oracle and still did not get anywhere.

Q1. basically how do you enable DISM on Solaris 8 and Oracle 9iR2, provided that we really get some memory benefits as claimed by Oracle in the above quotation ? Q2. do you know of any sites that have implemented it and it is works fine for them ? it has been suggested to me that DISM is not what it claims, i.e it is no more than growing/shrinking SGA where SGA_MAX_SIZE is the upper limit. But that is not what we are after here. Any help is appreciated. Samir Saad.

-- Samir Saad (saad.samir@saugov.sa.gov.au), December 16, 2002

Answers

activating DISM (dynamic intimate shared memory) to support Oracle in a Solaris8 environment is a bad idea because Solaris8 only supports small pagesizes (ie. 8kb) using standard ISM.

You are asking for large page support (4mb), but large page support is NOT support by Solaris for DISM until Solaris9.

Using smaller page sizes and attempting to run DISM causes the MMU to get the crap kicked out of it (huge performance hit).

Upgrade to Solaris9 before activating DISM.

-- Craig Irwin (craig.irwin@sun.com), October 18, 2004.