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rollback internals

Submitted by Kamil Stawiarski on Wed, 2017-09-20 16:33

While researching redo log internals for V00D00 we had to face the fact, that we know shit about real transactional behavior. When I say "real", I mean – under the hood.
Even with a very simple stuff like COMMIT and ROLLBACK we were constantly amazed by the internal mechanisms.

Today let’s take ROLLBACK under the investigation. According to documentation:

The ROLLBACK statement ends the current transaction and undoes any changes made during that transaction.

Cool. But what it means? First of all, you have to realize that all changes in redo logs are in a form of REDO RECORD which has its own address, known as RBA or RS_ID.

Sample RS_ID (RBA) looks like this: 0x00000a.00008c0f.006c

When UPDATE becomes an INSERT

Submitted by Kamil Stawiarski on Mon, 2017-07-24 20:46

During a research for VOODOO, we came across a lot of interesting stuff inside REDO.
One of my favourites is an UPDATE, becoming an INSERT </p /> </p></div> <div class=

When UPDATE becomes an INSERT

Submitted by oakroot on Mon, 2017-07-24 20:46

During a research for VOODOO, we came across a lot of interesting stuff inside REDO.
One of my favourites is an UPDATE, becoming an INSERT </p /> </p></div> <div class=

How to recover a dropped package from archivelogs – based on research for VOODOO engine

Submitted by Kamil Stawiarski on Sun, 2017-05-28 11:32

Sorry for long time without post, but we are writing with Marcin Rydz a new heterogenous replication product based on archivelogs and it’s consuming a looooooot of our time </p /> </p></div> <div class=

How to recover a dropped package from archivelogs – based on research for VOODOO engine

Submitted by oakroot on Sun, 2017-05-28 11:32

Sorry for long time without post, but we are writing with Marcin Rydz a new heterogenous replication product based on archivelogs and it’s consuming a looooooot of our time </p /> </p></div> <div class=

back to the basics: ALTER TABLE MOVE vs SHRINK

Submitted by Kamil Stawiarski on Wed, 2017-02-01 00:50

It’s time for the next article with ODBV visualisation </p /> </p></div> <div class=

back to the basics: ALTER TABLE MOVE vs SHRINK

Submitted by oakroot on Wed, 2017-02-01 00:50

It’s time for the next article with ODBV visualisation </p /> </p></div> <div class=

back to the basics: truncate table reuse storage vs drop storage

Submitted by Kamil Stawiarski on Fri, 2016-12-30 19:44

From time to time I get questions on my trainings, what is the difference between TRUNCATE TABLE and TRUNCATE TABLE DROP STORAGE… well, there is no difference because DROP STORAGE is default </p /> </p></div> <div class=

OTN Appreciation Day : pragma UDF

Submitted by Kamil Stawiarski on Tue, 2016-10-11 18:38

Joining the OTN Appreciation Day </p /> </p></div> <div class=

OTN Appreciation Day : pragma UDF

Submitted by oakroot on Tue, 2016-10-11 18:38

Joining the OTN Appreciation Day </p /> </p></div> <div class=