I think you might need to tell ADSM what to do (prune or delete).  Here is what 
I have in my dsm.sys file on an AIX client:

SErvername  adsm_mvs
   COMMmethod         TCPip
   TCPPort            1500
   TCPServeraddress   mvshost
   Passwordaccess     generate
   Inclexcl           /usr/lpp/adsm/bin/backup.excl
   schedlogretention  7 D
   schedlogname       /usr/lpp/adsm/bin/dsmsched.log
   errorlogretention  7 D
   errorlogname       /usr/lpp/adsm/bin/dsmerror.log
   Nodename           cws_x_svc
   TCPWindowsize      16

>>> Guy LaCreta <Guy_LaCreta AT MCKINSEY DOT COM> 5/11/98 3:30:24 PM >>>
Hi Guys,

We recently installed V3 of ADSM and when we try to start the admin client
with errorlogretention 7 set in the dsm.opt file we get the error:

ANS1038S Invalid option specified
ANS8009E Exiting due to command or option errors.

ANS8002I Highest return code was 400.

Has anybody running V3 ADSM experienced this? Is there a syntax change that
 IBM forgot to include in the on-line documentation.

AHIA, Guy