rdisp/max_child_procs is a SAP Parameter attribute which is used to control maximum number of processes that can be forked via popen information. This is available within R/3 SAP systems depending on the version and release level.
Below is the standard documentation available and a few details of the attributes values .
To execute operating system commands, for example, work processes
generate new operating system processes ("child" processes) in certain
situations. These are managed by the generating process. This parameter
defines the maximum number of child processes at any one time.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.