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Understanding Shared Memory and Semaphores

by Nidhi Jain

Shared memory and semaphores are two important resources for an Oracle instance on Unix. An instance cannot start if it is unable to allocate what it needs.

Protecting Oracle executables on Unix

Execute the following commands to protect Oracle executables on Unix from unauthorized access:

cd $ORACLE_HOME/bin

chmod 750 lsnrctl
chmod 750 svrmgrl
chmod 750 orapwd
chmod 750 tnslsnr
chmod 750 dbshut
chmod 750 dbstart
chmod 750 tstshm
chmod 750 runInsaller

Also, change file permissions for all you Oracle database files:

Controlfiles = chmod 640 rw-r

Is my database/ OS running 32-bit or 64-bit software?

DBAs often need to know if they should install Oracle 32-bit or 64-bit software on a given server. If the operating system support 64-bit applications, the 64-bit Oracle distribution can be loaded. Otherwise, the 32-bit distribution must be installed. The following Unix commands will tell you whether your OS is running 32-bits or 64-bits:

Solaris - isainfo -v (this command doesn't exist on Solaris 2.6 because it is only 32-bits)

HP-UX - getconf KERNEL_BITS

AIX - bootinfo -K

If you need to know if Oracle 32-bit or 64-bit software is currently installed on a system, connect using a command line utility like sqlplus and look at the banner. If you are running 64-bit software, it will be mentioned in the banner. If nothing is listed, you are running on a 32-bit base.

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