UNIX Shell ScriptOracle Useful Information
SUN Kernal Parameters and Oracle
Posted : 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/systemDescription
        
      set semsys:seminfo_semmni=100Total 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=200This 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=200Total 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=10485760Higher 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=20Total no of shared memory segmentss per 
      process.
      set shmsys:shminfo_shmmin=1Minimum 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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