I am getting all of the following error first:

ORA-12162: TNS:net service name is incorrectly specified

When I export the ORACLE_SID , I can run any command and I get the following error:

connected to an idle instance

Where is the ALERTLOG file in 12C?

I can't see any file in ORACLE_HOME/log folder. I am using ubuntu 14.04 BTW.

  • I think the question is useful in terms of "where is the log file". But the sub-question about the idle instance should just be removed from this question to improve the quality, no?
    – Wouter
    Dec 3, 2015 at 9:56

3 Answers 3


The alert log never has been under ORACLE_HOME/log.

It is in $ORACLE_BASE/diag/rdbms/<sid>/<sid>/trace and is named alert_<sid>.log

If you don't have $ORACLE_BASE, this typically is equivalent to $ORACLE_HOME/../../..

This is no different in 12c than it was in 11g (or 10g if I recall correctly).

You can also use the ADRCI tool: http://docs.oracle.com/database/121/SUTIL/adrci.htm#SUTIL1474


alert log find better way;------

step 1

select * from v$diag_info;

step 2

$ORACLE_BASE/diag/rdbms/<sid>/<sid>/trace and is named alert_<sid>.log


desc v$diag_info

Name                                                                Null?    Type
 ------------------------------------------------------------------- -------- ---------------
 INST_ID                                                                      NUMBER
 NAME                                                                         VARCHAR2(64)
 VALUE                                                                        VARCHAR2(512)
 CON_ID                                                                       NUMBER

Quick sql*plus script to get it out

-- diag_info
-- quick check of the new v$diag_info view that came in with 11
col inst_id form 9999 head inst
col name form a25
col value form a60 wrap
spool diag_info.lst
set lines 120
select * from v$diag_info
order by name
spool off

INST_ID NAME                 VALUE                                                            CON_ID
-------- -------------------- ---------------------------------------------------------------- -------
       1 Diag Enabled          TRUE                                                                  0
       1 ADR Base              D:\APP\ORACLE                                                         0
       1 ADR Home              D:\APP\ORACLE\diag\rdbms\ora122\ora122                                0
       1 Diag Trace            D:\APP\ORACLE\diag\rdbms\ora122\ora122\trace                          0
       1 Diag Alert            D:\APP\ORACLE\diag\rdbms\ora122\ora122\alert                          0
       1 Diag Incident         D:\APP\ORACLE\diag\rdbms\ora122\ora122\incident                       0
       1 Diag Cdump            D:\app\oracle\diag\rdbms\ora122\ora122\cdump                          0
       1 Health Monitor        D:\APP\ORACLE\diag\rdbms\ora122\ora122\hm                             0
       1 Default Trace File    D:\APP\ORACLE\diag\rdbms\ora122\ora122\trace\ora122_ora_7416.trc      0
       1 Active Problem Count  0                                                                     0
       1 Active Incident Count 0                                                                     0
    show parameter background;

will provide you path for alert log file.

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