Re: What information is stored in the redo change vectors exactly ?

A redo record is made up of one or more redo change vectors. A redo change vector describes a change to a block in the database.

For example, until 10g, a committed transaction that did a single update to an unindexed table would produce:

Change record 1

    change vector 1

        describing the acquisition of a slot in a rollback segment header Change record 2

    change vector 1

        describing previous version of material in the table block (plus some

        information about previous versions of data in the segment header)     change vector 2

        describing the new version of material in the table block Change record 3

    change vector 1

        describing the release of the slot in the rollback segment header
        (It is this record that is the 'commit record' described in the
        manuals)

A change vector typically holds information like:

    This is an 'update row piece' operation     The fourth column of the third row in the block should be 'X'     The lock byte for this row should be set to 3     The third ITL entry in the block should be set to 'yyyyyyyyy'

plus various bits of cross-reference material

-- 
Regards

Jonathan Lewis

http://www.jlcomp.demon.co.uk/faq/ind_faq.html
The Co-operative Oracle Users' FAQ

http://www.jlcomp.demon.co.uk/seminar.html
Public Appearances - schedule updated March 9th 2005






"Deepa balu via DBMonster.com" <forum_at_DBMonster.com> wrote in message 
news:e8121ef15d5c4017bca46291b5574bef_at_DBMonster.com...


>

> In concepts it is mentioned that "Redorecords are change vectors 

> describing

> a single atomic change to the database."

>

> So In case of recovery these redorecords are applied to recover the

> changes done.

>

> What exactly these redorecords contain.

>

> Do they contain all the queries,commit/rollback which are executed on the

> database

>

> What information is stored in the  vectors exactly ?

>

> -- 

> Message posted via http://www.dbmonster.com