Oracle 9i RMAN backup filling up all disk and failing at the very end

Question

Hello to all and thank you in advance for any input from any of you.
I am new in oracle and the only one in my company with a little bit of oracle knowledge, which is not a whole lot.
I inherited a few servers (Linux and Windows based). We mostly run all our production environment on a Linux box hosting oracle 10g release 10.2.0.1 but we had a legacy application server that still runs on 9i release 9.2.0.1.0. This server is a windows 2003 box, the previous DBA or someone else with admin rights to this machine compressed the whole drive where oracle resides, when I started summarying the oracle assets, I saw this server with no backups scheduled and a compressed disk with very limited space after this compression, only 13 GB left, the database if uncompressed would definitively filled up all the disk. The machine is in used and cannot be taken down for more than a couple of hours. We tried adding another disk but the machine only accept it as a hot spare. The database is in archive mode, when I tried to run a RMAN backup, it start filling up the database drive until it's empty and it crashes the whole machine, it seems like the buffer is growing and growing until it fills up the whole drive. The only way to get the server up and running again is to reboot the machine since the server is more than 6 years old we are not please with this action because we are afraid the machine would go south in one of those reboots.
Has anyone heard of similar issues when running RMAN on a compressed drive? Can the compressed disk have any involvement in this kind of odd behaviour? I tried running the backup in debug mode and creating a log in a different disk (the one where the backup is going to) and still the same issue. Again any help is much appreciate,
Sincerely,
Alex

Answer 1

Sybrand,
Thank you for your fast response, I am going to use your previous post to answer one by one your question,
1 The Oracle binaries --- on a compressed drive > Yes
2 The Oracle database control files redo log files and datafiles on that same compressed drive? > Yes
3 The archived redo log ditto? > Yes
I know for a fact (as I have been using that in 9i) you can create a RMAN backup on a compressed drive, and you can have your archived redo go to a compressed drive. No problemo! > Excellent good news!!!
But I would never touch the data files. Please note backup sets are multiplexed files consisting of multiple datafiles, so RMAN would need to do some calculations to decompress several blocks at the same time and to calculate a new block and compress it.
Do you have enough space to:
a) (preferred) to make datafile copies instead of a backup >
Not in the drive that hosts the oracle instance but yes on an external usb drive (1TB) I attached to use as a backup repository, maybe this is why I am having these issues. I only have 13 GB left on that drive where the oracle instance resides (actually as I explained in a previous reply to Mark, the server only has 3 slots for disks, two of them as configured as RAID 1 and the other is a hot spare because the RAID configuration manager cannot can only added as hot-spare. The raided disk are partitioned in two, one small partition is for the OS and the other is for the oracle instance). When you said make a copy of the datafiles, I assumed you are talking about doing manual backups, and copying the database after using using "alter tablespace tablespace_name begin backup; then copy the file; alter tablespace tablespace_name end backup;
b) use filesperset=1 on the backup command line, so the multiplexing (and associated calculations) stop. I have not tried the option of fileperset yet but I can tryi it and see if that helps.
Can you post the last few lines of the RMAN log where RMAN bombs out? Note: the last few lines. Not all of it, or you must send some paracetamol in conjunction! >
When I ran the debug option, I stopped the backup at less than 20% because I didn't want to reboot the system in the middle of the production time, the backup consumed at least 3 GB during the time was running. The times I ran the RMAN backup I didn't used the debug option so I don't have a log long enough to send unless you want the last few lines of what I have.
Thanks again for your input,
Sincerely,
Alex