The OPEN subcommand cannot start any more shell sessions. The maximum number of active shell sessions for this user has already been reached. The maximum number of sessions is determined by the value of MAXPROCUSER or CHILD_MAX. No additional sessions can be started if the number of sessions would exceed MAXPROCUSER/2.
End some other shell session before starting any new sessions.
Ask the system programmer to increase the value of MAXPROCUSER to allow more sessions. The value for MAXPROCUSER should be at least twice the number of active sessions required.