Got "INS-35075: The specified SID is already in use" error in Oracle, how to fix it?

Question

Cause
The Oracle system identifier (SID) given was already in use.
Action
Specify a unique Oracle system identifier (SID).

What is it cause? How could I fix it?

Answer 1

You can find here How to uninstall / completely remove Oracle 11g (client)?

• Uninstall all Oracle components using the Oracle Universal Installer (OUI).
• Run regedit.exe and delete the HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE key. This contains registry entires for all Oracle products.
• Delete any references to Oracle services left behind in the following part of the registry: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Ora* It should be pretty obvious which ones relate to Oracle
• Reboot your machine
• Delete the "C:\Oracle" directory, or whatever directory is your ORACLE_BASE
• Delete the "C:\Program Files\Oracle" directory.
• Empty the contents of your "C:\temp" directory
• Empty your recycle bin

Calling additional attention to some great comments that were left here: -Be careful when following anything listed here (above or below), as doing so may remove or damage any other Oracle-installed products. - For 64-bit Windows (x64), you need also to delete the HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\ORACLE key from the registry. - Clean-up by removing any related shortcuts that were installed to the Start Menu. - Clean-up environment variables: - Consider removing %ORACLE_HOME%. - Remove any paths no longer needed from %PATH%

This set of instructions happens to match an almost identical process that I had reverse-engineered myself over the years after a few messed-up Oracle installs, and has almost always met the need.

Note that even if the OUI is no longer available or doesn't work, simply following the remaining steps should still be sufficient.

Answer 2

In Red Hat 6.6 delete the respective line in the file /etc/oratab