restore database from dmp file I have a situation:
I have a dmp file and a database with old data
server crashed and the latest data we have ar in the dmp file!
we managed to pull the server back but it has old data!
so we need to restore from the dmp!
how to import back the database from dmp file and replace all data and structure (tables schemes)...

I know it's RMAN's job but we do not have it in place, and it's urgent case!
version, OS, tool are helping things to help you solve this. 

I guess OS is Windows.
version 9i.
export full.

If this is the case:
connect to the server,
set ORACLE_HOME=/where/is/oracle/home/
set PATH=%ORACLE_HOME%/bin;%PATH%
set ORACLE_SID=ORCL -> or your ORACLE_SID name

imp file=x.dmp logfile=imp_x.log full=y


imp help=y gives some clues about the commandline options.

study the errors. If there is a complaint about the dmp file, read the first few blocks. From those you can find who exported it, what type export it is and even some version info. It is a bit binary but just readable enough to get this info.

tip:

If your data has a real value for your company, hire a real dba to make a decent setup and have someone as a backup. It is easy to build a system that work happily for years and due to hardware issues suddenly become less happy. It's a pity if that costs your company the head. This is regardless for what brand of database you setup.