关于参数 _ktb_debug_flags & _smu_debug_mode

ALLSTARS_ORACLE

keyword = _ktb_debug_flags
On Standby, DBV Shows Pages Failing With Check Code 6056 (Doc ID 1523623.1)

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Actually, as written in Note:8895202.8 :

_ktb_debug_flags=8 NEEDS TO REMAIN in the database to ENABLE THE FIX.

You can set it this way:
% sqlplus / as sysdba
SQL> alter system set "_ktb_debug_flags"=8;

-> Blocks are repaired when they are cleaned out.

Trace file may show a message like:
Healing Corrupt DLC ITL objd:%d objn:%d tsn:%d rdba:<rdba> itl:%d
option:%d xid:<xid> cmtscn:<scn> curscn:<scn>

-> There is no danger in keeping _ktb_debug_flags=8 all the time.
It just gets triggered on by invalid scn in itl.

Notes:
The patch should be applied to both primary and standby and the parameter set on both.
"_ktb_debug_flags"=8 does not have performance impact.
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keyword = _smu_debug_mode=134217728


How to disable cleanout optimization (Doc ID 1066674.1)
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Cleanout optimization can be disabled by setting the following parameter:

_smu_debug_mode=134217728

This is a bit mask setting which can be set dynamically if necessary.
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Minact-Scn Master-Status: Grec-Scn Messages In Trace File (Doc ID 1361567.1)
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"_smu_debug_mode=134217728"


After setting above parameter the message will not be generated but This will disable min active SCN optimization feature.

"min active scn" introduced in 11g which is supposed to enhance delayed block cleanout operations. Note : - Disabling min active scn optimization feature will not have any impact on database.
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INIT.ORA Parameter: "_smu_debug_mode" [Hidden] (Doc ID 563556.1)
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Description:
~~~~~~~~~~~~
This parameter allows you to generated trace output around automatic undo segments
(AUM) activity or to change the behavior of AUM.

The parameter can be set to a decimal number that corresponds to a bit string of
flags described below (these were derived out of code comments and some flags have
not yet been confirmed by inspecting code and filed bugs).


0x08000000 disable MinActiveSCN feature


       
关于_ktb_debug_flags，该参数仅仅作为一个trigger来获得ITL中的invalid SCN ，可以长期使用，没有任何影响。

具体信息，请参考
On Standby, DBV Shows Pages Failing With Check Code 6056 (Doc ID 1523623.1)

----
Actually, as written in Note:8895202.8 :

_ktb_debug_flags=8 NEEDS TO REMAIN in the database to ENABLE THE FIX.

You can set it this way:
% sqlplus / as sysdba
SQL> alter system set "_ktb_debug_flags"=8;

-> Blocks are repaired when they are cleaned out.

Trace file may show a message like:
Healing Corrupt DLC ITL objd:%d objn:%d tsn:%d rdba:<rdba> itl:%d
option:%d xid:<xid> cmtscn:<scn> curscn:<scn>

-> There is no danger in keeping _ktb_debug_flags=8 all the time.
It just gets triggered on by invalid scn in itl.

Notes:
The patch should be applied to both primary and standby and the parameter set on both.
"_ktb_debug_flags"=8 does not have performance impact.
------


关于 _smu_debug_mode=134217728 的设置，该参数的介绍如下

This parameter allows you to generated trace output around automatic undo segments
(AUM) activity or to change the behavior of AUM.

The parameter can be set to a decimal number that corresponds to a bit string of
flags described below (these were derived out of code comments and some flags have
not yet been confirmed by inspecting code and filed bugs).


0x08000000 disable MinActiveSCN feature 《====转换为10进制的值为 134217728。

该参数设置对数据库也没有任何影响。

更多信息，请参考


Minact-Scn Master-Status: Grec-Scn Messages In Trace File (Doc ID 1361567.1)
------
"_smu_debug_mode=134217728"


After setting above parameter the message will not be generated but This will disable min active SCN optimization feature.

"min active scn" introduced in 11g which is supposed to enhance delayed block cleanout operations. Note : - Disabling min active scn optimization feature will not have any impact on database.
------