This matches the data I have collected, with the following addition: RMAN will backup any blocks that have ever had data in them, even if the extent has been deallocated or the object dropped.
Keith ----- Original Message ----- To: "Multiple recipients of list ORACLE-L" <[EMAIL PROTECTED]> Sent: Friday, April 04, 2003 10:13 AM > What it doesn't write are the blocks that are not allocated to any > extent. RMAN doesn't go into the logical structures, like tables and > indexes, > it looks into the tablespace header and reads the information from the > bitmap information there. It cannot go into tables/indexes because it > should also work when the database is only mounted and not opened, which > genrally means that data dictionary is not accessible. Empty blocks > are blocks that don't have any rows in them but are allocated to an > extent. New or unallocated blocks are blocks that have been initialized > when the datafile was allocated to the tablespace but have not been assigned > to any object (table, index, materialized view, cluster, partition or alike) > > -----Original Message----- > Sent: Thursday, April 03, 2003 4:24 PM > To: Multiple recipients of list ORACLE-L > > > Actually this is how RMAN works. It writes all blocks up to the HWM of a > given table, > even empty ones. So, if your HWM is artifically high, you will encounter > backups > that are larger than they need to be. > > Oracle9i RMAN Backup and Recovery.... On bookshelves now! > > RF > > > -----Original Message----- > To: Multiple recipients of list ORACLE-L > Sent: 4/3/2003 11:19 AM > > Keith > Here is my understanding (don't rely on this one). When Oracle > allocates > tablespace, the disk blocks are cleared. My interpretation is that when > RMAN > encounters a clear block, it doesn't write it to the backup piece. I > don't > think it spends a lot of time trying to figure out above HWM and such. > > Dennis Williams > DBA, 40%OCP, 100% DBA > Lifetouch, Inc. > [EMAIL PROTECTED] > > > -----Original Message----- > Sent: Thursday, April 03, 2003 10:44 AM > To: Multiple recipients of list ORACLE-L > > > Our RMAN backup is backing up much more than the actual data blocks when > doing a full backup. I know that it backs up all blocks that have "ever > been > used", but I'm trying to figure out exactly what that means. My first > thought was that it backs up all blocks below the HWM, but I analyzed > the > tables and that is not the case. > > Sometimes it backs up more blocks than exist below the HWM for the > tables > and sometimes it backs up fewer blocks than those below the HWM. > > We are doing this to determine what we can do to reduce the size of the > backup. > > Anyone have an idea how this works? > > Keith > > > -- > Please see the official ORACLE-L FAQ: http://www.orafaq.net > -- > Author: DENNIS WILLIAMS > INET: [EMAIL PROTECTED] > > Fat City Network Services -- 858-538-5051 http://www.fatcity.com > San Diego, California -- Mailing list and web hosting services > --------------------------------------------------------------------- > To REMOVE yourself from this mailing list, send an E-Mail message > to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in > the message BODY, include a line containing: UNSUB ORACLE-L > (or the name of mailing list you want to be removed from). You may > also send the HELP command for other information (like subscribing). > -- > Please see the official ORACLE-L FAQ: http://www.orafaq.net > -- > Author: Freeman Robert - IL > INET: [EMAIL PROTECTED] > > Fat City Network Services -- 858-538-5051 http://www.fatcity.com > San Diego, California -- Mailing list and web hosting services > --------------------------------------------------------------------- > To REMOVE yourself from this mailing list, send an E-Mail message > to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in > the message BODY, include a line containing: UNSUB ORACLE-L > (or the name of mailing list you want to be removed from). You may > also send the HELP command for other information (like subscribing). > -- > Please see the official ORACLE-L FAQ: http://www.orafaq.net > -- > Author: Gogala, Mladen > INET: [EMAIL PROTECTED] > > Fat City Network Services -- 858-538-5051 http://www.fatcity.com > San Diego, California -- Mailing list and web hosting services > --------------------------------------------------------------------- > To REMOVE yourself from this mailing list, send an E-Mail message > to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in > the message BODY, include a line containing: UNSUB ORACLE-L > (or the name of mailing list you want to be removed from). You may > also send the HELP command for other information (like subscribing). > >
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