Oracle Database Cannot Open mount Mode Error: ORA-01102

Error in opening mount mode of database: ora-01102: cannot mount database in exclusive mode

SQL> startup nomount;
 
ORACLE instance started.

Total System Global Area 1073741824 bytes
Fixed Size		    2932632 bytes
Variable Size		  427819112 bytes
Database Buffers	  629145600 bytes
Redo Buffers		   13844480 bytes
SQL> SQL> alter database mount;
 
alter database mount
*
ERROR at line 1:
ORA-01102: cannot mount database in EXCLUSIVE mode

Reason: There is a “sgadef.dbf” file in the “ORACLE_HOME/dbs” directory and Oracle processes (pmon, smon, lgwr, and dbwr) still exist – even if the database is closed, the shared memory segments and semaphores still exist – there is an “ORACLE_HOME/dbs/lk” file “lk” and “sgadef. There is an “ORACLE_HOME/dbs/lk” file “lk” and “sgadef. dbf ” files for locking shared memory. It seems that even if no memory is allocated, Oracle thinks the memory is still locked.
To view the startup log:


Solution.
1. Go to /d01/oracle/PROD/db/tech_st/12.1.0/dbs/ directory
2. Delete the lkPOD file

rm -rf  lkPROD

3. Make sure Oracle has no background processes: ps -ef |grep ora_ |grep PROD|grep ora_dbw0_PROD

if there is a background process, please use the command “kill” to delete it.

[[email protected] ~]$  kill -9 1912

Log in again using mount mode

[[email protected] ~]$ sqlplus/as sysdba

SQL*Plus: Release 12.1.0.2.0 Production on Wed Mar 2 12:52:42 2022

Copyright (c) 1982, 2014, Oracle.  All rights reserved.

Connected to an idle instance.

SQL> startup mount
ORACLE instance started.

Total System Global Area 1073741824 bytes
Fixed Size		    2932632 bytes
Variable Size		  427819112 bytes
Database Buffers	  629145600 bytes
Redo Buffers		   13844480 bytes
Database mounted.

Successfully resolved.

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