If you are keeping your system up to date with Patchsets, Patch Bundles, Merge Label Requests (MLR) or Critical Patch Updates (CPU), you will most likely suffer from a huge .patch_storage Subdirectory in your $ORACLE_HOME.

On one of my databases it looked like this:

Space used by $ORACLE_HOME: 7 GB
Space used by $ORACLE_HOME/.patch_storage: 4.3 GB

Can data in this directory be removed?

MetaLink Note 550522.1 (Subject: How To Avoid Disk Full Issues Because OPatch Backups Take Big Amount Of Disk Space.) has the answer and tells you: it depends. Normally, this data is used in order to be able to rollback a patch. However, if you have installed a patchset (eg. 10.2.0.4), then the patches for the previous patchset (10.2.0.3) which are located in the .patch_storage directory are not needed anymore and can be removed. However, I would not recommend that you delete the directories manually yourself, as this would not be supported. Instead let Oracle do it for you:

Recent versions of opatch (current is 10.2.0.4.5 as of January 2009) have a utility included, which removes patches not needed anymore from the .patch_storage directory. Moreover, the opatch utility creates these .patch_storage backup directories more intelligently which should result in less space wasted.

[oracle@vmhost1 ora10]$./OPatch/opatch util Cleanup
Invoking OPatch 10.2.0.4.5

Oracle Interim Patch Installer version 10.2.0.4.5
Copyright (c) 2008, Oracle Corporation. All rights reserved.

UTIL session

Oracle Home : /oracle/ora10
Central Inventory : /oracle/oraInventory
from : /var/opt/oracle/oraInst.loc
OPatch version : 10.2.0.4.5
OUI version : 10.2.0.4.0
OUI location : /oracle/ora10/oui
Log file location : /oracle/ora10/cfgtoollogs/opatch/opatch2009-01-15_17-00-51PM.log

Patch history file: /oracle/ora10/cfgtoollogs/opatch/opatch_history.txt

Invoking utility “cleanup”
OPatch will clean up ‘restore.sh,make.txt’ files and ‘rac,scratch,backup’ directories.
You will be still able to rollback patches after this cleanup.
Do you want to proceed? [y|n]
y
User Responded with: Y
Size of directory “/oracle/ora10/.patch_storage” before cleanup is 4575330012 bytes.
Size of directory “/oracle/ora10/.patch_storage” after cleanup is 188326505 bytes.

UtilSession: Backup area for restore has been cleaned up. For a complete list of files/directories
deleted, Please refer log file.

OPatch succeeded.

180 MB instead of 4 GB. I like that.