ORA-01102: cannot mount database in exclusive mode

I got ” ORA-01102: cannot mount database in exclusive mode ”  error in Oracle database.

ORA-01102: cannot mount database in exclusive mode

Details of error are as follows.

ORA-01102 cannot mount database in EXCLUSIVE mode

Cause: Some other instance has the database mounted exclusive or shared.
Action: Shut down the other instance or mount in a compatible mode.

SQL> alter database mount;
alter database mount
*
ERROR at line 1:
ORA-01102: cannot mount database in EXCLUSIVE mode
SQL>

cannot mount database in EXCLUSIVE mode

This ORA-01102 errors are related with the Some other instance has the database mounted exclusive or shared.

Shut down the other instance or mount in a compatible mode.

Firstly shutdown instance using the shutdown immediate command.

Then kill ALL Oracle process using the following script.

[oracle@msdbadm01 ~]$ kill -9 `ps -ef | grep $ORACLE_SID | grep -v grep | awk '{print $2}'`

Now run startup mount again.

SQL> startup mount;
ORACLE instance started.

Total System Global Area 895105620 bytes
Fixed Size 2022504 bytes
Variable Size 163578776 bytes
Database Buffers 415236096 bytes
Redo Buffers 6365184 bytes
Database mounted.


SQL> alter database open;

Database altered

If you use Oracle RAC, then set cluster_database parameter to true and run it again as follows.

alter system set cluster_database=TRUE scope=spfile sid='*';
shutdown immediate;
srvctl start database -d DB_NAME

Do you want to learn Oracle Database for Beginners, then read the following articles.

Oracle Tutorial | Oracle Database Tutorials for Beginners ( Junior Oracle DBA )