TSM备份oracle归档日志，过期删除问题

TSM这边的副本组配置为1000，备份后的数据在带库上保留31天。但是发现归档日志31天内的会被删除。有哪位朋友遇到过吗？

删除脚本（31天前的数据删除）：

configure retention policy to recovery window of  31 days;

delete noprompt obsolete DEVICE TYPE 'sbt_tape';

delete noprompt obsolete;

4月17日的输出日志看到删除了3月29日的数据：

RMAN retention policy is set to recovery window of 31 days

Deleting the following obsolete backups and copies:

Type                 Key    Completion Time    Filename/Handle

-------------------- ------ ------------------ --------------------

Backup Set           584    29-MAR-17         

  Backup Piece       584    29-MAR-17          hls0crej_1_1

Backup Set           585    29-MAR-17         

  Backup Piece       585    29-MAR-17          hms0crh9_1_1

deleted backup piece

backup piece handle=hls0crej_1_1 RECID=584 STAMP=939945427

deleted backup piece

backup piece handle=hms0crh9_1_1 RECID=585 STAMP=939945513

Deleted 2 objects