ORA-01102: cannot mount database in EXCLUSIVE mode

[code]SQL> startup
ORACLE instance started.

Total System Global Area 167772160 bytes
Fixed Size 1218316 bytes
Variable Size 71305460 bytes
Database Buffers 92274688 bytes
Redo Buffers 2973696 bytes
ORA-01102: cannot mount database in EXCLUSIVE mode


[oracle@localhost oracle]$ cd /oracle/product/database/dbs/
[oracle@localhost dbs]$ ls
hc_pstc.dat initdw.ora lkPSZX_DB spfilepstc.ora
hc_pszx_db.dat init.ora orapwpstc spfilepszx_db.ora
[oracle@localhost dbs]$ fuser -u lkPSZX_DB
-bash: fuser: command not found
[oracle@localhost dbs]$ su -
Password:
[root@localhost ~]# cd /oracle/product/database/dbs/
[root@localhost dbs]# fuser -u lkPSZX_DB
lkPSZX_DB: 6699(oracle) 6701(oracle) 6703(oracle) 6705(oracle) 6707(oracle) 6709(oracle) 6711(oracle) 6713(oracle) 6715(oracle) 6717(oracle) 6719(oracle) 6727(oracle) 6744(oracle) 6746(oracle) 6749(oracle) 6751(oracle) 6782(oracle) 7425(oracle) 9953(oracle) 10032(oracle) 10034(oracle)
[root@localhost dbs]# fuser -k lkPSZX_DB
lkPSZX_DB: 6699 6701 6703 6705 6707 6709 6711 6713 6715 6717 6719 6727 6744 6746 6749 6751 6782 7425 9953 10032 10034
[root@localhost dbs]# fuser -u lkPSZX_DB



SQL> startup
ORA-01081: cannot start already-running ORACLE - shut it down first
SQL> shutdown
ORA-01507: database not mounted


ORACLE instance shut down.
SQL> startup
ORACLE instance started.

Total System Global Area 167772160 bytes
Fixed Size 1218316 bytes
Variable Size 71305460 bytes
Database Buffers 92274688 bytes
Redo Buffers 2973696 bytes
Database mounted.
Database opened.
SQL> [/code]