Re: Oracle Data Recovery

"Tim Mason" <tlmason840_at_aol.com> wrote

> The Oracle database files reside on the D: Last week an NT admin
> crashed both system and had to rebuild the systems C:, this also wiped
> out the installation of Oracle. We have been unable to access the ORA
> files. We originally attempted to create a table space and point it
> at an existing ORA file. This action appeared to clear the ora file
> and was stopped before it deleted all the data. Is there a way to
> recover the data from these ORA files? If there is can anyone give me
> any pointers as to how to do this.

I am not sure what you mean with "attempted to create a table space and point it at an existing ORA file" Tom. Hopefully it means that you tried to use a datafile belonging to the "crashed database" in a new database (which will not work btw!), in which case Oracle would have said that it could not create the file as it already exists. No damage should have resulted.

Assuming that the Oracle database files on drive D: survived untouched, all you need to is install Oracle on drive C: and bring the database up. Hopefully you simply need to recreate the initXXX.ora file on drive C: (in which case you can use the sample init.ora that Oracle provides with a couple of minor modifications).

If your control files were also on C:, then you need to recreate those. This can be dangerous if you do not have a backup controlfile or a dump to trace.. But let's hope that you do have controlfiles on drive D:.

To backtrack a bit. If you only loose your Oracle system software, not a problem. The actual database will still intact. What you do loose with the system are things like the alert log files, the initXXX.ora file and so on. The main thing is that the database files on drive D: should have remained untouched. IOW, the actual physical datafiles which constitutes the database are okay. I.e.the datafiles used for the system, temp and user tablespaces, the datafiles used for the rollbacks, the control files, the redo logs and so on.

If this is the case, you still have a complete (and hopefully working) database. All that is missing :

1. the Oracle system software for creating a database engine (instance) for that database
2. the configuration file for the database engine (essentially telling it the location of the database control files which in turn points the database engine at the rest of the database files to open and use)

Note that it is basically impossible to recover data from a single Oracle database datafile on its own, without having the file spec format for that datafile and writing software to attempt to extract the data. This can be done by internal Oracle support (which I could get some of that internal documentation they carry around ;-).

However, you can _not_ create a new database and assign an old database's datafiles to it, hoping to recover the data that way.

Before attempting any recover, it is _imperative_ that a FULL PHYSICAL BACKUP be done of drive D: first. If you do screw something up during the recovery process, you always have the oppertunity to restore and attempt the recovery again.

Hopes this help.

--
Billy
PS. Apologies for misunderstanding your posting first time around. I was under
the impression you were attempting to recover the contents of drive D: