PSU patch

Hi All,

Could someone please explain the purpose of each steps involved below for applying PSU patch in Oracle database?

Pre- checks

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1)Check the listener status using command ps -ef|grep tns

2)Check the DB instance status using command ps -ef|grep pmon

3)select OWNER,OBJECT_NAME,OBJECT_TYPE,CREATED,LAST_DDL_TIME,STATUS from dba_objects where status='INVALID';

4)select count(*) from dba_indexes where status='UNUSABLE';

5)select count(*) from dba_ind_partitions where status='UNUSABLE';

6)select count(*) from dba_ind_subpartitions where status='UNUSABLE';

7)select * from registry$history;

8)select COMP_ID,COMP_NAME,VERSION,STATUS,MODIFIED from dba_registry;