ORA-600 [2662] Block SCN is ahead of Current SCN [ID 28929.1]

ORA-600 [2662] "Block SCN is ahead of Current SCN" [ID 28929.1]
	Modified 09-DEC-2010Type REFERENCEStatus PUBLISHED

Note: For additional ORA-600 related information please read Note:146580.1

PURPOSE:

This article discusses the internal error "ORA-600 [2662]", what

it means and possible actions. The information here is only applicable

to the versions listed and is provided only for guidance.

ERROR:

ORA-600 [2662] [a] [b] [c] [d] [e]

VERSIONS:

versions 6.0 to 10.1

DESCRIPTION:

A data block SCN is ahead of the current SCN.

The ORA-600 [2662] occurs when an SCN is compared to the dependent SCN

stored in a UGA variable.

If the SCN is less than the dependent SCN then we signal the ORA-600 [2662]

internal error.

ARGUMENTS:

Arg [a] Current SCN WRAP

Arg [b] Current SCN BASE

Arg [c] dependent SCN WRAP

Arg [d] dependent SCN BASE

Arg [e] Where present this is the DBA where the dependent SCN came from.

FUNCTIONALITY:

File and IO buffer management for redo logs

IMPACT:

INSTANCE FAILURE

POSSIBLE PHYSICAL CORRUPTION

SUGGESTIONS:

There are different situations where ORA-600 [2662] can be raised.

It can be raised on startup or duing database operation.

If not using Parallel Server, check that 2 instances have not mounted

the same database.

Check for SMON traces and have the alert.log and trace files ready

to send to support.

Check the SCN difference [argument d]-[argument b].

If the SCNs in the error are very close, then try to shutdown and startup

the instance several times.

In some situations, the SCN increment during startup may permit the

database to open. Keep track of the number of times you attempted a

startup.

If the Known Issues section below does not help in terms of identifying

a solution, please submit the trace files and alert.log to Oracle

Support Services for further analysis.

Known Issues:

Bug# 5889016 See Note:5889016.8

Corruption / OERI during recovery

Fixed:

Bug# 4453449 See Note:4453449.8

OERI:3020 / corruption errors from multiple FLASHBACK DATABASE

Fixed: 10.2.0.2, 11.1.0.6

Bug# 2899477 See Note:2899477.8

Minimise risk of a false OERI[2662]

Fixed: 9.2.0.5, 10.1.0.2

Bug# 2764106 See Note:2764106.8

False OERI[2662] possible on SELECT which can crash the instance

Fixed: 9.2.0.5, 10.1.0.2

Bug# 2216823 See Note:2216823.8

OERI [2662] reusing a TEMPFILE with a restored database

Fixed: 10.1.0.2

Bug# 2054025 See Note:2054025.8

OERI:2662 possible on new TEMPORARY index block

Fixed: 9.0.1.3, 9.2.0.1

Bug# 851959 See Note:851959.8

OERI:2662 possible from distributed OPS select

Fixed: 7.3.4.5

Bug# 647927 P See Note:647927.8

Digital Unix ONLY: OERI:2662 could occur under heavy load

Fixed: 8.0.4.2, 8.0.5.0

INTERNAL ONLY SECTION - NOT FOR PUBLICATION OR DISTRIBUTION TO CUSTOMERS

========================================================================

There were 2 forms of this error until 7.2.3:

Type I: 4/5 argument forms -

The SCN found on a block (dependent SCN) is ahead of the

current SCN. See below for this

Type II: 1 Argument (before 7.2.3 only):

Oracle is in the process of writing a block to a log file.

If the calculated block checksum is less than or equal to 1

(0 and 1 are reserved) ORA-600 [2662] is returned.

This is a problem generating an offline immediate log marker

(kcrfwg).

*NOT DOCUMENTED HERE*

Type I

~~~~~~

a. Current SCN WRAP

b. Current SCN BASE

c. dependent SCN WRAP

d. dependent SCN BASE

e. Where present this is the DBA where the dependent SCN came from.

From kcrf.h:

If the SCN comes from the recent or current SCN then a dba

of zero is saved. If it comes from undo$ because the undo segment is

not available then the undo segment number is saved, which looks like

a block from file 0. If the SCN is for a media recovery redo (i.e.

block number == 0 in change vector), then the dba is for block 0

of the relevant datafile. If it is from another database for a

distributed transaction then dba is DBAINF(). If it comes from a TX

lock then the dba is really usn<<16+slot.

Type II

~~~~~~~

a. checksum -> log block checksum - zero if none (thread # in old format)

---------------------------------------------------------------------------

Diagnosis:

~~~~~~~~~~

In addition to different basic types from above, there are different

situations where ORA-600 [2662] type I can be raised.

Getting started:

~~~~~~~~~~~~~~~~

(1) is the error raised during normal database operations (i.e. when the

database is up) or during startup of the database?

(2) what is the SCN difference [d]-[b] ( subtract argument 'b' from arg 'd')?

(3) is there a fifth argument [e] ?

If so convert the dba to file# block#

Is it a data dictionary object? (file#=1)

If so find out object name with the help of reference dictionary

from second database

(4) What is the current SQL statement? (see trace)

Which table is refered to?

Does the table match the object you found in previous step?

Be careful at this point: there may be no relationship between DBA in [e]

and the real source of problem (blockdump).

Deeper analysis:

~~~~~~~~~~~~~~~~

(1) investigate trace file:

this will be a user trace file normally but could be an smon trace too

(2) search for: 'buffer'

("buffer dba" in Oracle7 dumps, "buffer tsn" in Oracle8/Oracle9 dumps)

this will bring you to a blockdump which usually represents the

'real' source of OERI:2662

WARNING: There may be more than one buffer pinned to the process

so ensure you check out all pinned buffers.

-> does the blockdump match the dba from e.?

-> what kind of blockdump is it?

(a) rollback segment header

(b) datablock

(c) other

Check list and possible causes

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

If Parallel Server check both nodes are using the same lock manager

instance & point at the same control files.

Possible causes:

(1) doing an open resetlogs with _ALLOW_RESETLOGS_CORRUPTION enabled

(2) a hardware problem, like a faulty controller, resulting in a failed

write to the control file or the redo logs

(3) restoring parts of the database from backup and not doing the

appropriate recovery

(4) restoring a control file and not doing a RECOVER DATABASE USING BACKUP

CONTROLFILE

(5) having _DISABLE_LOGGING set during crash recovery

(6) problems with the DLM in a parallel server environment

(7) a bug

Solutions:

(1) if the SCNs in the error are very close, attempting a startup several

times will bump up the dscn every time we open the database even if

open fails. The database will open when dscn=scn.

(2)You can bump the SCN either on open or while the database is open

using <Event:ADJUST_SCN> (see Note:30681.1).

Be aware that you should rebuild the database if you use this

option.

Once this has occurred you would normally want to rebuild the

database via exp/rebuild/imp as there is no guarantee that some

other blocks are not ahead of time.

Articles:

~~~~~~~~~

Solutions:

Note:30681.1 Details of the ADJUST_SCN Event

Note:1070079.6 Alter System Checkpoint

Possible Causes:

Note:1021243.6 CHECK INIT.ORA SETTING _DISABLE_LOGGING

Note:41399.1 Forcing the database open with `_ALLOW_RESETLOGS_CORRUPTION`

Note:851959.9 OERI:2662 DURING CREATE SNAPSHOT AT MASTER SITE

Known Bugs:

~~~~~~~~~~~

Fixed In. Bug No. Description

---------+------------+----------------------------------------------------

7.1.5 BUG:229873

7.1.3 Bug:195115 Miscalculation of SCN on startup for distributed TX ?

7.1.6.2.7 Bug:297197 Port specific Solaris OPS problem

7.3 Bug:336196 Port specific IBM SP AIX problem -> dlm issue

7.3.4.5 Bug:851959 OERI:2662 possible from distributed OPS select

Not fixed Bug:2216823 OERI:2662 reported when reusing tempfile with restored DB

8.1.7.4 Bug:2177050 OERI:729 space leak possible (with tags "define var info"/"oactoid info")

can corrupt UGA and cause OERI:2662

---------------------------------------------------------------------------

Ensure that this note comes out on top in Metalink when searched

ora-600 ora-600 ora-600 ora-600 ora-600 ora-600 ora-600

ora-600 ora-600 ora-600 ora-600 ora-600 ora-600 ora-600

2662 2662 2662 2662 2662 2662 2662 2662 2662

2662 2662 2662 2662 2662 2662 2662 2662 2662

</Internal_Only

Related

---

Products

---

· Oracle Database Products > Oracle Database > Oracle Database > Oracle Server - Enterprise Edition

· Oracle Database Products > Oracle Database > Oracle Database > Oracle Server - Personal Edition

· Oracle Database Products > Oracle Database > Oracle Database > Oracle Server - Standard Edition

Keywords

---

BUGTAG_ADDBUGS; INTTEAMREVIEWED; NOTDDRCONFIRMED

Errors

---

ORA-600[2662]

------------------------------------------------------------------------------

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