Missing AWR snapshots ...

Hello All,

DB Version : 11.1.0.7
OS : RHEL 5

We take AWR snapshots for every 30 minutes and keep for 365 days. We have noticed some missing snapshots, in one of our production databases. Please see the output attached from awrrpt.sql.

What could cause such a thing to happen? Any help would be appreciated.

Thanks in advance.
Satish



Instance     DB Name        Snap Id    Snap Started    Level
------------ ------------ --------- ------------------ -----
eid1         EID1             22387 09 Aug 2010 00:00      1
                              22388 09 Aug 2010 00:30      1
                              22389 09 Aug 2010 01:00      1
                              22391 09 Aug 2010 02:01      1
                              22393 09 Aug 2010 03:02      1
                              22397 10 Aug 2010 05:14      1
                              22398 10 Aug 2010 05:30      1
                              22399 10 Aug 2010 06:01      1
                              22400 10 Aug 2010 06:30      1
                              22401 10 Aug 2010 07:00      1
                              22402 10 Aug 2010 07:32      1
                              22405 10 Aug 2010 09:01      1
                              22406 10 Aug 2010 09:30      1
                              22407 10 Aug 2010 10:00      1
                              22408 10 Aug 2010 10:30      1
                              22409 10 Aug 2010 11:00      1
                              22410 10 Aug 2010 11:30      1
                              22411 10 Aug 2010 12:00      1
                              22412 10 Aug 2010 12:30      1
                              22413 10 Aug 2010 13:00      1
                              22414 10 Aug 2010 13:30      1
                              22415 10 Aug 2010 14:00      1
                              22416 10 Aug 2010 14:30      1
                              22417 10 Aug 2010 15:00      1
                              22418 10 Aug 2010 15:30      1
                              22419 10 Aug 2010 16:00      1
                              22420 10 Aug 2010 16:30      1
                              22421 10 Aug 2010 17:00      1
                              22422 10 Aug 2010 17:30      1
                              22423 10 Aug 2010 18:00      1
                              22424 10 Aug 2010 18:30      1