You did not specify what type of server SAPDB is running on, but, I would check that server, and see if there are any hanging processes, specifically
sapdbbar
sapdb_backint
util_sapdb
Also, check for
vbda
vrda
bma
rma
mma
Kill any of these that you see
Whether or not you see any hanging processes, stop and restart DP at a time when nothing is running, and run
/opt/omni/sbin/omnidbutil -clear
If none of this helps, you will probably need to open a case for this problem