how RMAN expires backup (retention)

three types of retentions are there
1.redudancy retention
2.recovery window retention
3.keep until retention

1.redudancy retention:here the one database backup will be kept always as REDUNDANCY is 1 o

when we take a proper new backup the last one will become obsolete

rman>show all;
CONFIGURE RETENTION POLICY TO REDUNDANCY 1; # default

rman>show all;
rman>list backup;
rman>report obsolete;
rman> backup database plus archivelog;
rman>list backup;

rman>show all;
CONFIGURE RETENTION POLICY TO REDUNDANCY 1; # default

rman>report obsolete;

rman>delete obsolete;

rman>list backup summary;

rman> backup database plus archivelog;

rman>list backup summary;

rman>list backup;

rman>delete noprompt obsolete;
####################################### recovery window
################

eg 3 days window

rman >show all;

#change policy from redundancy(default) to recovery window

rman>configure retention policy to recovery window of 3 days;
rman >show all;
rman>report obsolete;
rmn>list backup;
rman>backup database plus archivelog;
rman>list backup summary;---4files
rman>report obsolete;

if todays is 20 date sun
#change date to 21 mon

rman>backup database plus archivelog;
rman>list backup summary;-----8files
rman>report obsolete;

#change date to 22--tuesday

rman>backup database plus archivelog;
rman>list backup summary;-----12files
rman>report obsolete;

#change date to 23 --wed

rman>report obsolete;

you will see the backup obolete and archivelog also plus meta data
#currently archivelog seq

rman>backup database plus archivelog;
rman>list backup summary;-----16files
rman>report obsolete;

#change date to 24 --wed

rman>report obsolete;

obsolete things are
archivelog seq + backup piece + archivelog seq

rman>delete obsolete;

rman>report obsolete;

nothing is obsolete now.

keep until

rman> backup database keep until time 'sysdate+7';

this overrites the set value of the retention for this backup

and make it obsolete oon the 8th day