Server level 3.1.2.0 added a new message to warn that this was happening.
You could use it to trigger some action like increasing the trigger value to 
stop
another backup from starting immediately, or start a process to increase the
size of the log, or shut down the server.

When I have seen this problem, it is usually related to a very long running 
backup.

The new message is --

ANR4556W Warning: the database backup operation
did not free sufficient recovery log
space to lower utilization below the
database backup trigger. The recovery
log size may need to be increased.
Explanation:  A database backup process
has completed. The server is running in
roll-forward mode and the recovery log
utilization remains above that specified in
the database backup trigger.
System Action:  A database backup
operation will be triggered. Unless this
situation is corrected, database backups
will be triggered rapidly, one after the other.
User Response:  If a database backup
operation does not free up enough
recovery log space to reset utilization
below the database backup trigger, the
recovery log needs to be extended or the
database backup trigger updated to a
higher log full percentage.

--
--------------------------
--------------------------
Bill Colwell
Bill Colwell
C. S. Draper Lab
Cambridge, Ma.
bcolwell AT draper DOT com
--------------------------
In <36C2EDC0.917849E AT lrz-muenchen DOT de>, on 02/11/99
In <36C2EDC0.917849E AT lrz-muenchen DOT de>, on 02/11/99
   at 03:48 PM, Werner Baur <Werner.Baur AT LRZ-MUENCHEN DOT DE> said:

>I have a similar problem with one of our larger servers.
>The server holds a 50 GB database.

>The latest crash occured this morning. The recovery log exceeded the limit
>of 75%. The triggered database backup did not free up sufficient space, db
>backup started again and so on. Normally we stop the server before we run
>out of recovery log space. This morning, 5:00 am, nobody was present to do
>it.
>So the server crashed. After the restart everything was fine.

>The server holds a 50 GB database. The recovery log is 4 GB.
>At the time of the first crash the trigger was set to 50%.  Following the
>recommendation of the error message text we increased the trigger to 75%.
>All the same the db looping continued.
>I have an open record for this problem.

>Werner


>Joel Fuhrman wrote:

>> AIX 4.2.1
>> ADSM Server level 3.1.2.13
>>
>> I have defined my dbbackuptrigger to be 50%.  The max log shows 57%.  When
>> the trigger was activated, it failed to reduce the log to less than 50%.  Is
>> this a bug?
>>
>> As the backups continued, it triggered additional dbbackups. Eventually, the
>> activity log is flooded with these messages:
>> 1999-02-09 03:06:40      ANR9999D logread.c(179): Attempt to read LSN
>>                           18717.193.3351 below trunc LSN 18768.171.991.
>>
>> Finally, the system paging space filled and processes were killed by AIX
>> which had the effect of killing ADSM.  Has any one else seen this behavior?
>>
>> ADSM is the only thing running on this system.  The paging space is normally
>> only 22% used.

>--
>Werner Baur                    Tel.:++49-89-28928781
>Leibniz-Rechenzentrum           Fax:++49-89-2809460
>Barer Str. 21                mailto:baur AT lrz DOT de
>D-80333 Muenchen, Germany      http://www.lrz.de