Re: Oracle Shared Memory Problem (DEC UNIX 4.0)

If shmmax is not large enough oracle will allow the SGA to cross shmmax boundries. The only limitation is that the fixed and variable (shared pool primarily) cannot traverse boundries (default on Digital is 4mb). The rest of the SGA , data cache, log buffer can certainly traverse shmmax boundries (not recommended).

You problem is attaching shared memory segments which is related but a different issue. Oracle attaches shared memory segments (4mb segments on digital unix) to support the SGA. oracle can attach upto shm-seg (32 default) segments . After that oracle may swap SGA in excess of what it can attach.

Assuming you have enough real memory, check your swap space. UNIX in an IMMEDIATE MODE swap configuration must have enough swap space to back the virtual address space required by the process starting up , namely oracle. If you do not have enough swap (in IMMEDIATE MODE) to back the virtual address space (the SGA) oracle will not attach the shared memory segments.

you can change digital unix swapping to deferred mode or add more swap 3-4 times real.

hope this helps a little.

Brian dougherty
chief database architect DBVision /
Oracle Education performance and tuning instructor bdoughe364_at_aol.com Received on Sat Dec 06 1997 - 00:00:00 CST