How to find out if Oracle is Installed in server

Question

I apologize for the simple question but no one in here seems to know if our server has Oracle installed or not. I have no experience in Oracle and have root access to the server but dont know the command to check wether Oracle is installed or not! anyone?
I thank you in advance for any help
Eduardo

Answer 1

This is one of those questions that can be a bit difficult to answer, given all the possibilities in the world. Since you said the magic word "root" I will assume you are on unix or at least a posix system.
http://tahiti.oracle.com has installation guides, find the one for your platform and check that. It should give a good foundation of what you want to look for. But some people get creative and some things are decisions by the DBA.
Since oracle may be installed and not running, looking for oracle processes may not tell you if oracle is installed. But a ps|grep ora can often give clues. It is even possible to delete files while oracle is running... (I've seen oracle uninstalled - it keeps running but new users can't log in. This is because rm a file doesn't actually remove a file until everyone is done with it.) Also, check ipcs - shared memory being used by oracle is a clue oracle is installed and/or running, but even that can be misleading with some configurations - sometimes a bungled startup will leave a mess.
Many unix systems have clues in /etc or /var/opt. Look for files with names like oratab and oraenv. Look at your passwd and group files, see if there are users with names like 'oracle' and groups like 'dba'. Look at user .profile, .cshrc, .bashrc, .kshrc files and see if there are references to oracle environment setting. $ORACLE_BASE, $ORACLE_HOME, $ORACLE_SID are often good clues, as well as references to oraenv or similar names. Look at the system startup files and see if there are references to oracle: there could be things like /sbin/rc*/*ora*, /etc/rc.d/*/*ora*, and so forth. Often the rc directories have a link to an init directory, such as a file like /sbin/init.d/oracle. There may be an inventory around somewhere called oraInventory, perhaps under $ORACLE_BASE, and installation log files, check your install guide for names. Also, if you have found $ORACLE_HOME and $ORACLE_SID in an oratab, you might check $ORACLE_BASE/admin/$ORACLE_SID/bdump/alert*log. Be aware that $ORACLE_HOME and the "oracle home directory" probably are not the same.
Older systems that have been clumsily dealt with may have all these things, and yet still not have "oracle installed." Good luck.
For these reasons and more, usually you would want to specify exact platform and oracle versions.
Edit: fixed alert log location