When I installed Oracle 9i ( on RedHat Linux (AS 3), the installation went OK. But when the DBCA started to create the database, the error message "ORA-27123: unable to attach to shared memory segment" was produced. I cannot have any database installed in my machine. I really do not know what is wrong. Your help will be greatly appreciated.

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You are receiving this error either because your kernel parameters are not set correctly, or the SGA of the database the DBCA is attempting to create is too large to fit into the available physical memory segments.

First, check that the kernel parameters are as follows:

SHMMAX = 2147483648
SHMMNI = 100
SEMMNS = 1000
SEMMSL = 250
SEMMNI = 100
SEMOPM = 100

Refer to the installation guide on Oracle's Technology Network Web site for an explanation of each of these parameters.

If the parameters have been set correctly, lower the memory requirements for the database being created. This will create a smaller SGA which may allow the database creation to complete successfully.

This was first published in March 2006

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