$ORACLE_HOME
$ORACLE_BASE
$ORACLE_SID
also check /etc/hosts file it must contains correct hostname and ip.
example:
[oracle@oel6 ~]$ sqlplus / as sysdba SQL*Plus: Release 11.2.0.3.0 Production on Mon Jan 27 11:55:17 2014 Copyright (c) 1982, 2011, Oracle. All rights reserved. Connected. SQL> startup; ORA-01012: not logged on SQL> shutdown immediate; ORA-00000: normal, successful completion SQL> shutdown abort; ORACLE instance shut down. SQL> startup; ORA-00000: normal, successful completion
after that i checked environment variables:
[oracle@oel6 ~]$ echo $ORACLE_BASE /u0/app/oracle [oracle@oel6 ~]$ echo $ORACLE_HOME /u0/app/oracle/product/11.2.0/dbhome_1 [oracle@oel6 ~]$ echo $ORACLE_SID orcl
it's correct, then checked /etc/host file
cat /etc/hosts #10.10.1.176 oel6
bingo! someone maybe system administrator or other dba commented this machine hostname and ip, hence we can't start database, uncomment it and everything goes correct.
vi /etc/hosts 10.10.1.176 oel6 sqlplus / as sysdba SQL*Plus: Release 11.2.0.3.0 Production on Mon Jan 27 12:03:10 2014 Copyright (c) 1982, 2011, Oracle. All rights reserved. Connected to an idle instance. SQL> startup; ORACLE instance started. Total System Global Area 835104768 bytes Fixed Size 2232960 bytes Variable Size 645926272 bytes Database Buffers 180355072 bytes Redo Buffers 6590464 bytes Database mounted. Database opened.
