ORA-27123 unable to attach shared memory segment

Question

Running oracle 8.1.5.0.0 on Redhat 6.0 with kernel 2.2.12, I keep getting the error ORA-27123 unable to attach shared memory segment when trying to startup and instance with an SGA > 150 MB or so. I have modified the shmmax and shmall kernel parameters via the /proc/sys interface. The relevant output of ipcs -l is below:
------ Shared Memory Limits --------
max number of segments = 128
max seg size (kbytes) = 976562
max total shared memory (kbytes) = 16777216
min seg size (bytes) = 1
This system has 2gb of physical memory and is doing nothing except oracle.
I changed the shmmax and shmall parameters after the instance was created, was their something I needed to do to inform Oracle of the changes?

Answer 1

High JW,
i had the same problem on my installation.
The solution is written in the Oracle8i Administrator Refernece on page 1-26 "Relocating the SGA"
a) determine the valid adress range for Shared Memory with:
$ tstshm
in the output Lowest & Highest SHM indicate the valid adress range
b) run genksms to generate the file ksms.s
$ cd $ORACLE_HOME/rdbms/lib
$ $ORACLE_HOME/bin/genksms -b "sga_beginn_adress" > ksms.s
c) shut down any instance
d) rebuilt the oracle exe in $ORACLE_HOME/rdbms/lib
$ make -f ins_rdbms.mk ksms.o
$ make -f ins_rdbms.mk ioracle
the result is a new oracle kernel that loads the SGA at the adress specified in "sga_beginn_adress".
regards
Gerhard