THis subject has been heavily discussed already. Just search ADSM-L for details.
By the way, if I have Oracle database mydb on sever MYNODE and dedicated TSM 
node MYNODE_ORA for TDPO backups then:

1) on TSM Server:
  Policy        Policy          Mgmt                          Copy              
    Versions     Versions      Retain         Retain
Domain        Set Name   Class                           Group                 
Data           Data            Extra           Only
Name                             Name                          Name             
     Exists         Deleted       Versions     Version
---------     ---------     ---------                       ---------           
   --------      --------       --------      -------
AIX           ACTIVE        AIX                           STANDARD      No 
Limit     No Limit      32              32
AIX           ACTIVE        MYNODE_ORA      STANDARD       1                0   
               0                0

2) From RMAN on server MYNODE (example for AIX node, $RC_USER, $RC_PASSWORD and 
$RC_SERVICE are for recovery catalog database):
#!/bin/sh
#
export ORACLE_SID=mydb
export ORACLE_BASE=/home/oracle
export ORACLE_HOME=`grep "mydb:" /etc/oratab | head -n1 | cut -f2 -d":"`
export PATH=$ORACLE_HOME/bin:$PATH
export TNS_ADMIN=$ORACLE_HOME/network/admin
#
# Configure backup policy
rman <<EOF
#
# Connect to Recovery Manager Catalog Database
connect catalog $RC_USER/$RC_PASSWORD@$RC_SERVICE;
#
# Connect to target database
connect target;
#
# Set retention policy
CONFIGURE RETENTION POLICY TO RECOVERY WINDOW OF 60 DAYS;
EOF
exit

In this case RMAN will manage TDPO backups to provide possibility to recover 
database to any time during last 60 days.
Note only this way is correct.


________________________________________
From: ADSM: Dist Stor Manager [ADSM-L AT VM.MARIST DOT EDU] On Behalf Of 
Sujatha chk [tsm-forum AT BACKUPCENTRAL DOT COM]
Sent: Thursday, January 21, 2010 10:42 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: [ADSM-L] Data retention period 60days

Hi Gurus,

we backup our oracle database using rman to TAPE by TSM media management. 
Currently  Backup Retention policy has been set to 30 days. Please guide me on 
how to configure Back up Retention period to 60 days?

-Sujatha

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