DB2 UDB (Propagatable) Log records: Undo/Redo/Compensation/Normal: Explanation, subtypes, events

Bernard Dhooghe

The (limited to propagatable since version 9) log records are described
in the API reference manual.

What is meant by: normal/undo/redo/compensation records, what are the
possible subtypes for each of these record, what events trigger there
creation and when are they propagatable?

Remark: I believe this should be part of the documentation.
Bernard Dhooghe

Jan 25 '07 #1

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Knut Stolze

Bernard Dhooghe wrote:

The (limited to propagatable since version 9) log records are described
in the API reference manual.

What is meant by: normal/undo/redo/compensation records, what are the
possible subtypes for each of these record, what events trigger there
creation and when are they propagatable?

I can't answer all the questions, but here are a few pointers:

When you run an INSERT statement, data is written to data pages, indexes are
updated etc. This is written as _normal_ log record. The log records
include the data that is inserted. In case of a DELETE, the before image
is written.

Now let's do a ROLLBACK. DB2 has to undo the previous INSERT/DELETE. To
that end, DB2 goes through the log records of the transaction being rolled
back, figures out what had been done and compensates the changes. I'm not
exactly sure what counts as _undo_ and what as _compensation_ log record,
though.

Remark: I believe this should be part of the documentation.

Have you used the Feedback button in the online reference already?

--
Knut Stolze
DB2 z/OS Utilities Development
IBM Germany

Jan 25 '07 #2

Bernard Dhooghe

I've (just) send the posting to db*****@ca.ibm.com.

Bernard Dhooghe

On Jan 25, 10:32 pm, Knut Stolze <sto...@de.ibm.comwrote:

Bernard Dhooghe wrote:
The (limited to propagatable since version 9) log records are described
in the API reference manual.

What is meant by: normal/undo/redo/compensation records, what are the
possible subtypes for each of these record, what events trigger there
creation and when are they propagatable?I can't answer all the questions, but here are a few pointers:

When you run an INSERT statement, data is written to data pages, indexes are
updated etc. This is written as _normal_ log record. The log records
include the data that is inserted. In case of a DELETE, the before image
is written.

Now let's do a ROLLBACK. DB2 has to undo the previous INSERT/DELETE. To
that end, DB2 goes through the log records of the transaction being rolled
back, figures out what had been done and compensates the changes. I'm not
exactly sure what counts as _undo_ and what as _compensation_ log record,
though.

Remark: I believe this should be part of the documentation.Have you used the Feedback button in the online reference already?

--
Knut Stolze
DB2 z/OS Utilities Development
IBM Germany

Jan 26 '07 #3

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