To increase/decrease the number of workprocesses, value to be changed accordingly for the following parameters as per workprocess in RZ10 Transaction.
rdisp/wp_no_dia (for dialog workprocess)
rdisp/wp_no_btc ( for background workprocess)
rdisp/wp_no_spo (for spool workprocess)
rdisp/wp_no_enq (for enqueue workprocess)
rdisp/wp_no_vb (for update workprocess)
rdisp/wp_no_vb2 (for update2 workprocess)
In RZ10 transaction, select the profile of the instance, for which workprocess number to be changed and edit the profile through extended maintenance and save the changes done and activate the profile.
Please note that as this parameter is not dynamic one, restart of the application server is required for the changes to become effective.