Rman and Flash Recover questions.

Question

I am trying to understand some of the new features of Oracle 10g as they relate to backup and recovery.
1) Flashback Query? I have looked thru many technical bulletins in the Oracle Technology Network and Metalink and am still confused as from where Flashback Query retrieves the data. Documentation seems to point to the Undo Tablespace. Is this is true I assume the Undo Tablespace would have to be quite large if you wanted to retrieve a record that might be > 1 week old on an active database. The undo_retention parm would have to be set quite large and the Undo Tablespace would have to be created with the "Retention Guarantee" clause. Correct?
2) Backing Up the Flash Recovery Area to Tape?
For all databases we backup with Rman this is the standard backup configuration we use for Oracle 9i.
RMAN> show all;
RMAN configuration parameters are:
CONFIGURE RETENTION POLICY TO RECOVERY WINDOW OF 100 DAYS;
CONFIGURE BACKUP OPTIMIZATION OFF; # default
CONFIGURE DEFAULT DEVICE TYPE TO 'SBT_TAPE';
CONFIGURE CONTROLFILE AUTOBACKUP OFF; # default
CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE SBT_TAPE TO '%F'; # default
CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '%F'; # default
CONFIGURE DEVICE TYPE 'SBT_TAPE' PARALLELISM 2;
CONFIGURE DEVICE TYPE DISK PARALLELISM 1; # default
CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE SBT_TAPE TO 1; # default
CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default
CONFIGURE ARCHIVELOG BACKUP COPIES FOR DEVICE TYPE SBT_TAPE TO 1; # default
CONFIGURE ARCHIVELOG BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default
CONFIGURE MAXSETSIZE TO UNLIMITED; # default
CONFIGURE SNAPSHOT CONTROLFILE NAME TO '/crs01/app/oracle/product/9.2/dbs/snapcf_CRSP.f'; # default
The standard Rman backup script we use is seen below.
run {
# Full database backup including the control file and spfile
backup database format '%d_%U' ;
# Switch logs before backing up the archive logs
sql 'alter system archive log current';
# Backup all the archive logs for the past 5 days
backup archivelog from time 'sysdate-5' format '%d_archives_%U';
# Mark unavailable backups as expired
crosscheck backup;
# Delete backups older than 100 days
delete noprompt obsolete;
delete expired backup;
# Delete archive logs older than 7 days
delete noprompt archivelog until time 'SYSDATE-7';
# Backup control file again
backup current controlfile;
resync catalog;
If we use Flash Recovery area and have enough disk space for two days of Rman backups to be stored there we must move anything over two days old to tape. The command "Backup Recovery Area" backs up the Rman backups in the Flash area to tape, correct? Will any of the
configuration or backup commands listed above have to change? Upon execution of the Restore command in Rman will Rman know to retrieve from tape a backup > 2 days old?
Thanks

Answer 1

Hi David
1.yes u need large undo tablespace that hold information for long time.
and set undo retension parameter according to need of flashback query.
But Don't set "Retention Guarantee" because when u set this parameter it will fail DML transaction on database.
because it will give importance to retail data in undo.
In simple Scenerio(No Guarantee Mode)
if DML required undo space in undo tablespace then it will overwrite expired undo and select query may be fail with "snapshot too old error"
But when u set it to undo retension then
oracle will not able overwrite on expired undo and u r DML query fail..........
so in normal prod database we will give more importance on DML query rather then Select query
so Don't use undo retension to gurantee mode.
But u can use in dataware house where query take long time to fetch result even in days.
2.u need to config MML for taking backup of rman to tape directly.
Thanks and regards
Kuljeet Pal Singh