ORA-00600: [ktbdchk1: bad dscn]

Last week I had performed switchover activity of database on version 11.2.0.3 The switchover was performed using dgmgrl “swicthover to standby” command. After sometime we started receiving “ORA-00600: [ktbdchk1: bad dscn]” on the primary database.

Tue Dec 16 10:33:26 2014
Errors in file /ora_software/diag/rdbms/db02_dbv/dbv/trace/db02_ora_16271.trc  (incident=434103):
ORA-00600: internal error code, arguments: [ktbdchk1: bad dscn], [], [], [], [], [], [], [], [], [], [], []
Incident details in: /ora_software/diag/rdbms/db02_dbv/dbv/incident/incdir_434103/db02_ora_16271_i434103.trc

The trace file showed

*** ACTION NAME:() 2014-12-16 10:33:26.857

Dump continued from file: /ora_software/diag/rdbms/db02_dbv/dbv/trace/db02_ora_16271.trc
ORA-00600: internal error code, arguments: [ktbdchk1: bad dscn], [], [], [], [], [], [], [], [], [], [], []

========= Dump for incident 434103 (ORA 600 [ktbdchk1: bad dscn]) ========
----- Beginning of Customized Incident Dump(s) -----
[ktbdchk] -- ktbgcl4 -- bad dscn
dependent scn: 0x0008.f197f24e recent scn: 0x0008.c7313a4c current scn: 0x0008.c7313a4c
----- End of Customized Incident Dump(s) -----
*** 2014-12-16 10:33:26.961
dbkedDefDump(): Starting incident default dumps (flags=0x2, level=3, mask=0x0)
----- Current SQL Statement for this session (sql_id=dmrpvzvbbsuy5) -----
INSERT INTO MSG_OPEN( SITE_ID, CLIENT_ID, CAMP_ID, MESSAGE_ID, ID, USER_ID, ADDRESS, DATE_OPENED) VALUES( :B7 , :B6 , :B5 , :B4 , LOG_SEQ.NEXTVAL, :B3 , :B2 , :B1 )
----- PL/SQL Stack -----
----- PL/SQL Call Stack -----
  object      line  object
  handle    number  name
0x32276ee18       611  package body TP.EM_PKG
0x31cbac388         3  anonymous block
----- Call Stack Trace -----
calling              call     entry                argument values in hex
location             type     point                (? means dubious value)
-------------------- -------- -------------------- ----------------------------
skdstdst()+36        call     kgdsdst()            000000000 ? 000000000 ?
                                                   7FFFFDA13028 ? 000000001 ?
                                                   000000001 ? 000000002 ?
ksedst1()+98         call     skdstdst()           000000000 ? 000000000 ?
                                                   7FFFFDA13028 ? 000000001 ?
                                                   000000000 ? 000000002 ?
ksedst()+34          call     ksedst1()            000000000 ? 000000001 ?
                                                   7FFFFDA13028 ? 000000001 ?
                                                   000000000 ? 000000002 ?
dbkedDefDump()+2741  call     ksedst()             000000000 ? 000000001 ?
                                                   7FFFFDA13028 ? 000000001 ?
                                                   000000000 ? 000000002 ?
........................

Searching for the issue on Metalink pointed to the below Document:-

ALERT Description and fix for Bug 8895202: ORA-1555 / ORA-600 [ktbdchk1: bad dscn] ORA-600 [2663] in Physical Standby after switchover (Doc ID 1608167.1)

As per metalink

In a Data Guard environment with Physical Standby (including Active Data Guard), invalid SCNs can be introduced in index blocks after a switchover.

Symptoms

ORA-1555 / ORA-600 [ktbdchk1: bad dscn] / ktbGetDependentScn /  Dependent scn violations as the block ITL has higher COMMIT SCN than block SCN.

DBVERIFY reports the next error when the fix of Bug 7517208 is present; reference Note 7517208.8 for interim patches:


itl[] has higher commit scn(aaa.bbb) than block scn (xx.yy)
 Page  failed with check code 6056

There is NO DATA CORRUPTION in the block. 

To Resolve

The fix of Bug 8895202 is the workaround.

Although the fix of Bug 8895202 is included in patchset 11.2.0.2 and later, the fix needs to be enabled by setting parameter _ktb_debug_flags = 8.

SQL> alter system set "_ktb_debug_flags"=8 scope=both sid='*';

System altered.

SQL> exit

If you are using Oracle version less than 11.2.0.2, then rebuilding index is the option, as we did for one of the client on 11.1.0.7 version.

One thing to note is –

In rare cases blocks healed by this fix may cause queries to fail with an ORA-600 [ktbgcl1_KTUCLOMINSCN_1] as described in Note 13513004.8 / Bug 13513004.

For more detail Metalink Doc 1608167.1