Operating system call fork:restart failed (error no. 22)

I got this message (see title) on my ERP 6.0 EhP6 system this morning and did find in the dev_disp it was due to an error on a workprocess. Only problem was, in my system I have 46 process (total) but it complained on workprocess 47, which we don't have. Now I narrowed it down to being a dynamic workprocess which can be created in a busy system or when deadlocks come up.

But what I do not understand is the following: It does complain in the dev_disp ERROR => DpWpCreate: restart of work process 47 prohibited by parameter as4/wp_max_restart (22: Invalid argument) but that parameter is not set nor known by RZ11.

Parameter setting:

rdisp/wp_max_no is set as DEFAULT

rdisp/max_dynamic_wp_alive_time is not set

rdisp/wp_no_restricted has the default value of 0

as4/wp_max_restart not known so not set

rdisp/wp_no_dia   = 28

rdisp/wp_no_vb    = 6

rdisp/wp_no_vb2  = 1

rdisp/wp_no_enq  = 1

rdisp/wp_no_btc   = 7

rdisp/wp_no_spo  = 3

Further error message info according to dev_disp:

*** ERROR => DpWpCreate: restart of work process 47 prohibited by parameter as4/wp_max_restart (22: Invalid argument) [dpu
***LOG Q0I=> DpWpCreate, fork ( fork:restart 22) [dpuxdisp.c   978]
*** ERROR => DpWpDynCreate: DpWpCreate [dpuxdisp.c   320]
*** ERROR => DpWpStartWp: DpWpDynCreate [dpxxwp.c     3434]
*** ERROR => DpWpDynamicCheck: failed to start dynamic W47 (rc=-1) [dpxxwp.c     3403]
*** ERROR => DpWpCreate: restart of work process 47 prohibited by parameter as4/wp_max_restart (22: Invalid argument) [dpu
***LOG Q0I=> DpWpCreate, fork ( fork:restart 22) [dpuxdisp.c   978]
*** ERROR => DpWpDynCreate: DpWpCreate [dpuxdisp.c   320]
*** ERROR => DpWpStartWp: DpWpDynCreate [dpxxwp.c     3434]
*** ERROR => DpWpDynamicCheck: failed to start dynamic W47 (rc=-1) [dpxxwp.c     3403]

*** WARNING => DpHdlDeadWp: wp_adm slot for W47 has no pid [dpxxwp.c     1681]

I cannot find any deadlocks, nor errors on priv workprocess of full processes during the period the errors came up and needed a dynamic workprocess.

Does any one have an idea on why this is coming up? And what to do about it to not show in SM21 (better, not getting this error) as it will pop up to me from Solution Manager monitoring (mail alert).

Note this morning it pop uped during a time frame from 7 to 8:30.