I have installed Oracle9i on Windows 2000 server and created a database. Everything was working fine until system admins changed the IP address of the windows 2000 database server. Now the database is not accessible and giving the error "ORA-12505 SID can not be resolved" error. I could not even connect to the database on the server itself as SYSDBA. Should I have to recreate the listener service? If the IP address of the database server changes, will I have to reinstall the database? Please advise.
I think your issue should be easy to resolve. Using a text editor, look at the listener.ora file in %ORACLE_HOME%networkadmin and see what's listed in the ADDRESS section for the HOST. If you have the old IP address there, then change it. If a hostname appears there, then verify that the hostname is actually the new IP address of your system. I'd use the "nslookup newhostname" command from a command prompt and see what IP address your hostname resolves to. I'm betting that either the DNS wasn't updated to match your hostname with the new IP address or you have an "old" IP address listed in your listener.ora.
One final check is to make sure that your hosts file doesn't have your hostname mapped to an incorrect IP address. This is a rare occurrence on Windows platforms, but worth a check. If you have a hosts file, it will be located in %SYSTEMROOT%system32driversetc and will be named hosts (no extension). You can open the hosts file in a text editor like notepad.