Question:

How can I create a reservation to prevent jobs from running with a specific job attribute?

Solution:

Reservations support a JOBATTRLIST both in a STRCFG and via mrsvctl.

Example:

SRCFG[stopattr] JOBATTRLIST=!project,!hsk

Or on a command line

mrsvctl -c -t ALL -a jattr='!sysp' 
mrsvctl -c -t ALL -a jattr='!project' 

Your escapte sequence might be different due to the shell you use.