.patch_storage in RDBMS_HOME & GI_HOME

Can we delete .patch_storage in RDBMS_HOME & GI_HOME directoryy

Yes, Please follow the below document. read it very carefully before clearing the files

Is it necessary to keep the $ORACLE_HOME/.patch_storage directory after successful installation of a patch?

Yes, It is necessary to keep the $ORACLE_HOME/.patch_storage directory even after successful installation of a patch. 

Reason for ORACLE storing the patch binaries & patch information on .patch_storage directory

* When you apply an interim patch to an Oracle home, OPatch stores the patch information in $ORACLE_HOME/.patch_storage directory. Inside this directory, there are separate directories created for each patch applied to the Oracle home. Interim patches are bug fixes that are made available to customers in response to specific bugs. CPU (Critical Patch Update) is also a kind of. The latest CPU will rollback the previously applied CPU as CPU is cumulative. So this rollback information is from the .patch_storage directory.

* You may come across a bug conflict and might want to remove the conflicting patch during the patch installation. This process is known as patch rollback. During patch installation, OPatch saves copies of all the files that were replaced by the new patch before the new versions of these files are loaded and stores it in $ORACLE_HOME/.patch_storage/patch ID/. These saved files are called rollback files and are the key to making patch rollback possible.

To Clean up the .patch_storage directory, oracle has come up with option called 

"opatch util cleanup"  option, please read the below document.

How To Avoid Disk Full Issues Because OPatch Backups Take Big Amount Of Disk Space. [ID 550522.1]