There are several situations when an interim patch is required. The most common one is to apply patches that correct specific bugs which you have encountered. Another situation where software maintenance is required is when Oracle releases the quarterly Critical Patch Update bundle. The patch task can consist of applying a single patch or several patches at once. Specific detailed instructions are always available in the companion README file.
Note
Never skip the README file and never take a patch for granted; you may face particular circumstances that, if neglected, may leave your software in an unstable condition.
In case something goes wrong or you want to uninstall the patch OPatch, always performs a backup of the affected files so you can apply a rollback procedure to return things to how they were when OPatch session has started.