SMON: ABOUT TO RECOVER UNDO SEGMENT %s messages in alert log

在alert日志中出现了下面的信息：

SMON: mark undo segment 70 as available

SMON: about to recover undo segment 70

SMON: mark undo segment 70 as available

SMON: about to recover undo segment 70

SMON: mark undo segment 70 as available

SMON: about to recover undo segment 70

SMON: mark undo segment 2 as available

SMON: about to recover undo segment 70

SMON: mark undo segment 1 as available

SMON: about to recover undo segment 70

SMON: mark undo segment 2 as available

SMON: about to recover undo segment 70

SMON: mark undo segment 1 as available

SMON: about to recover undo segment 70

SMON: mark undo segment 2 as available

SMON: about to recover undo segment 70

SMON: mark undo segment 1 as available

SMON: about to recover undo segment 70

SMON: mark undo segment 70 as available

Applies to:

Oracle Server - Enterprise Edition - Version: 8.1.5.0 to 9.2.0.8 - Release: 8.1.5 to 9.2

Information in this document applies to any platform.

***Checked for relevance on 24-Jan-2012***

Symptoms

There are lots of messages appearing in alert log of the following form

SMON: about to recover undo segment %s

SMON: mark undo segment %s as available

when instance recovery is performed after a abnormal shutdown.

Cause

These errors do not indicate rollback segment corruption.

Oracle 8i:

These messages indicate that there is a problem with the "rollback_segments" parameter in the init.ora.



Oracle 9i:

Automatic Undo management is being used. When the instance is shutdown, during the next startup instance recovery needs to take place.

In AUM we do not have any control over which undo segments will be brought online after the instance startup.

In case we require any of the offline undo segments for the instance recovery, these messages will appear in alert log.

This is not a bug but intended behavior.

When SMON finds such offline undo segments with transactions needing recovery, then it does what it is intended to do, i.e. perform the transaction recovery in batches of 100 undo records.

Solution

Oracle 8i:

Check that the rollback segment is included in the "rollback_segments" parameter. If not, adding the rollback segment and restarting the database will clear the problem.



Oracle 9i:

Solution 1:

To stop this messages from appearing you can use the workaround like below where 11 is the number that is appearing in the messages in the alert log.

SQL> alter session set "_smu_debug_mode"=4;

SQL> alter rollback segment "_SYSSMU11$" online;

Solution 2:

Apply patch set 9.2.0.6 or higher.

Please refer to

Note 3212131.8 - Bug 3212131 - Many 'undo segment' messages in the alert log

Solution 3:

Upgrade to 10g where the issue is removed with the new "Fast Ramp-Up" AUM feature.

Please refer to

Note 396863.1 - How to Keep All UNDO Segments from Being Offlined in Oracle 10g - Fast Ramp-Up

References

BUG:3418428 - ALERT.LOG FILLED WITH "SMON: ABOUT TO RECOVER UNDO SEGMENT 12" DURING TX RECOVER

NOTE:396863.1 - How to Keep All UNDO Segments from Being Offlined in Oracle 10g - Fast Ramp-Up

NOTE:3212131.8 - Bug 3212131 - Many 'undo segment' messages in the alert log

还有一种情况，：

Applies to:

Oracle Database - Enterprise Edition - Version 11.1.0.6 to 11.2.0.2 [Release 11.1 to 11.2]

Information in this document applies to any platform.

Symptoms

Huge smon trace is generated and to check why this big smon trace file is generated

-rw-r----- 1 ora3568 ems3568 706059 Nov 5 11:07 ems3568_smon_5130.trc

-rw-r----- 1 ora3568 ems3568 83146 Nov 5 11:07 ems3568_smon_5130.trm

SMON[TX-RECO]:about to recover undo segment 29 status:6 inst:2

SMON[TX-RECO]: mark undo segment 29 as available status:6 ret:3

SMON[TX-RECO]: mark undo segment 24 as available status:6 ret:1

SMON[TX-RECO]:about to recover undo segment 25 status:6 inst:2

Dead transaction 0x0019.019.000f3a94 recovered by SMON

SMON[TX-RECO]: mark undo segment 25 as available status:6 ret:1

SMON[TX-RECO]:about to recover undo segment 26 status:6 inst:2

Dead transaction 0x001a.021.00123692 recovered by SMON

SMON[TX-RECO]: mark undo segment 26 as available status:6 ret:1

SMON[TX-RECO]:about to recover undo segment 27 status:6 inst:2

Dead transaction 0x001b.01c.00127f7f recovered by SMON

Cause

Bug 10266152 : VERY LARGE SMON TRACE GENERATED W/ [SMON][TX-RECO] DEAD TRANSACTIONS

Solution

This Bug is fixed in 12.1 and 11.2.0.3

Please update to 11.2.0.3 or download and apply the
patch 10266152 if its available on top of your database version for your platform

workaround to stop the trace file from growing:

alter system set max_dump_file_size=10000 scope=both;

References

NOTE:1348303.1 - 11.2.0.3 Patch Set - List of Bug Fixes by Problem Type

NOTE:1440902.1 - In RAC SMON process Spinning & Huge Trace files With "domid 65535" messages are generated may show ORA-600 [kjsmbesmi:DDET!]

Description

Undo corruption may be caused after a shrink and the same undo block may be
used for two different transactions causing several internal errors like:

ORA-600 [4193] / ORA-600 [4194] for new transactions
ORA-600 [4137] for a transaction rollback

Undo segment shrink is internally done by Oracle.

This bug has an additional effect where SMON can spin to recover a transaction
with messages:

SMON: about to recover undo segment <usn>
SMON: mark undo segment <usn> as available

The affected undo segments shows some cycle in the block chain,
which causes the transaction recovery to spin.

This fix does not repair the current state of the undo segment.

Workaround
Drop the undo segment.

HOOKS OERI:4193 OERI:4194 OERI:4137 LIKELYAFFECTS XAFFECTS_10.2.0.1 XAFFECTS_V10020001 AFFECTS=10.2.0.1 XAFFECTS_10.2.0.2 XAFFECTS_V10020002 AFFECTS=10.2.0.2 XAFFECTS_10.2.0.3 XAFFECTS_V10020003 AFFECTS=10.2.0.3 XAFFECTS_10.2.0.4 XAFFECTS_V10020004
AFFECTS=10.2.0.4 XAFFECTS_11.1.0.6 XAFFECTS_V11010006 AFFECTS=11.1.0.6 XAFFECTS_11.1.0.7 XAFFECTS_V11010007 AFFECTS=11.1.0.7 XPRODID_5 PRODUCT_ID=5 PRODID-5 RDBMS XCOMP_RDBMS COMPONENT=RDBMS TAG_CORR TAG_CORR/LOG TAG_HANG/SPIN TAG_SMU CORR CORR/LOG HANG/SPIN
SMU FIXED_10.2.0.5 FIXED_11.1.0.7.10 FIXED_11.2.0.1 FIXED_WIN:A204P40 FIXED_WIN:B107P42

Please note: The above is a summary description only. Actual symptoms can vary. Matching to any symptoms here does not confirm that you are encountering this problem. For questions about this bug please consult Oracle Support.

References

Bug:8240762 (This link will only work for PUBLISHED bugs)

Note:245840.1 Information on the sections in this article