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Oracle Useful Information

SUN Kernal Parameters and Oracle

  

Updated : 2-November-1998
Version : 1.0

Description

This contains a short description and typical values of the SUN kernal parameters in relatin to Oracle databases.

Parameters

Change the Shared Memory parameters (/etc/system) from default to at least the following 
for one instance. For multiple instance on the same machine you need to recalculate some 
parameters.
Entry in /etc/system Description
   
set semsys:seminfo_semmni=100 Total no of semaphore set identifiers - determines the no of semaphores that can be created at one time. One identifier is required for each semaphore set.
set semsys:seminfo_semmns=200 This can be calculated by
Init Ora processes value + instance_processes + system processes
= value of the "processes" parameter in your initSID.ora file, controlling the total number of connections allowed to the database added up for ALL instances running on the system.
+ instance_processes = 5 (SMON, PMON, DBWR, LGWR and ARCH) multiplied by the number of instances running on the system.
+ system = number of semaphores required for non-Oracle processes, e.g. system and/or application processes, assume 50.
set semsys:seminfo_semmsl=200 Total no of semaphores in each set. On This should be the same as the highest value of processes of multiple instances. Oracle attempts to get 1 set containing processes semaphores).
set shmsys:shminfo_shmmax=10485760 Higher than the size of largest SGA on that machine.
set shmsys:shminfo_shmni=70 Shared memory identifiers 1 per segment attached by process.
set shmsys:shminfo_shmseg=20 Total no of shared memory segmentss per process.
set shmsys:shminfo_shmmin=1 Minimum size of shared segment (typically 1). 
After changing the parameters in /etc/system - reboot the machine
$ reboot
Check the shared memory parameters using 
$ sysdef -i
If they have not changed, load the shared memory module using 
$ modload /kernel/sys/shmsys

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