> Patch is a bug fix
> Collection of bug fixes is called a patch set
> Different types of patches released by oracle are:
1.Interim patch / one-off patch
3.Critical patch updates.
5.CRS Hash bundle patches
> All above patches can be installed using Opatch utility except Patchsets.
> Patchsets are installed by invoking runinstaller.
> CRS_HASH bundle patches are patches to fix the bugs in the cluster.
> Clusterware can be patched in two ways
>Incase of rolling upgrade we will bringdown all the services on then ode that we
wish to install the patch set.This is node by node activity.
>In case of non-rolling upgrade we bring down the entire cluster and install the patch set.
> To know the list of patches installed in CRS_HOME
$ Opatch lsinventory -detail $ORA_CRS_HOME
>To know the list of patches installed in ORACLE_HOME
$ opatch lsinventory -detail $ORACLE_HOME