A bundle patch is a cumulative collection of fixes for a specific product or component. A patch of this type is released as needed depending on the product's requirements. You may also know a bundle patch as: maintenance pack, service pack, MLRs, cumulative patch, or update release.
A diagnostic patch is designed to help diagnose or verify a fix or collection of bug fixes. You may also know a diagnostic patch as: test patch, Fix Verification Binary (FVB) or e-fix.
An interim patch provides a single bug fix, a collection of bug fixes, or a customer-specific security fix. They generally address specific bugs for a particular customer, and generally should not be applied unless instructed by Oracle Support to do so. You may also know an interim patch as: security one-off, exception release, x-fix, PSE, MLR, or hotfix.
The main way in which Oracle provides bug fixes in between releases. Oracle bundles a number of fixes, test them thoroughly together, and package them together for easy download and installation. They generally do not include new functionality and do not require a new certification. All of the fixes in the patch set have been tested and are certified to work with each other.
A collection of proactive, stabilizing cumulative patches for a particular product version (base release or patch set). PSUs are cummulative and include all of the security fixes from SPU patches (formerly known as CPU),plus additional fixes.
A security patch update is a cumulative collection of security-related bug fixes. Generally, security patch updates are release regularly. The security patch update was previously known as Critical Patch Update or CPU.
A patch is a piece of code/software designed to fix problems with the existing code/software. This includes fixing security vulnerabilities and other bugs, and improving the usability or performance.
If a patch makes different changes to the same section of code that another OPatch modifies, then these two patches conflict, and only one of them can be installed (unless a merge or overlay patch is available).
If a particular patch to be applied contains all of the fixes included in an already installed patch, plus additional fixes, then the patch with more fixes is a superset patch, and there is no conflict.
If a patch to be installed conflicts with more than one already installed patch, this is considered a combination conflict. In this case, OPatch will remove all conflicting patches then apply only the new patch.
Critical Patch Updates (CPUs) are the primary means of releasing security fixes for Oracle products. CPUs are cumulative with respect to prior CPUs and generall contain only security fixes.
A merge patch is one where multiple conflicting patches are combined into one integrated patch.
When an interim patch conflicts with a PSU, patch conflict resolution is achieved by providing a new patch that coexists with (and requires) the PSU patch. The new patch overlays the PSU, and the PSU is a pre-requisite for the overlay patch.
In a shared GI/RAC home, all nodes in the cluster use the same physical copy of the software. This simplifies configuration and management of many database operations because there is a single Home location rather than separate Homes on each node. When a GI Home or RAC Home is shared, individual nodes within the GI or RAC environments share a single file system and utilize a cluster file system such as Oracle Cluster File System 2 (OCFS2), in addition to sharing the same Home. Although this configuration is more disk space-efficient, the process of patching becomes a bit more complicated as the different nodes are utilizing the same resources/disk space.
Note: GI shared home installations can be patched only in non-rolling mode.
In a non-shared GI/RAC home, sometimes referred to as Private GI/RAC home, each node in the cluster maintains a complete copy of the Oracle software tree on local storage. This is the most common way in which Oracle Grid Infrastructure and Real Application Clusters are installed.