Reference to Metalink Doc 861152.1, to determine PSU version installed in your Oracle Home :-
1) Ensure that opatch version is having version of at least / or higher than :-
10.2.0.4.5 for version 10gR2 Oracle Home
11.1.0.6.5 for version 11gR1 Oracle Home
11.2.0.1.0 for version 11gR2 Oracle Home
For certain incident when even DBA / SYSDBA user can’t log-on, note that in 10g and above, there’s a lightweight sqlplus connection introduced. It’s called “preliminary connection”.
Two method to establish the preliminary connection in sqlplus :-
Upgrade steps for Oracle DB from 11.2.0.1 to 11.2.0.2 :
(1) Make sure you have taken level 0 database backup.
(2) Ensure that 11.2.0.2 (out-of-place) rdbms binary has been installed in new home e.g. /usr/oracle_gxs2/oracle/product/11.2/db_1.
(3) Please refer to Metalink / My Oracle Support document 1201253.1 to check for DST update action. In this scenario, we assume that no application schema object using datatype TSLTZ or TSTZ, hence no action on DST required.