Update work process trigger after user delete. saplscd4 program

Experts,

i delete user using FM BAPI_USER_DELETE or using SU01 TCode; if delete of users is in mass lets say 10-20 user; then i notice that multiple update(UP2) work process are created and seen in SM66. these work processes process user's CDHDR entries using program SAPLSCD4. this processing normally taking 5-7 minute of each work process.

Please advice what could be possible reason of work process taking so long time to process single user as multiple work processes are getting created simultaneously.

-Vivek