It is hard to understand what is happening on a system w/o more information. In a system, they normally operate on a round robin sort of flow so some things may be waiting for a system to free up. With loads of processes, and SAS jobs (in general), you are I/O bound.
Normally SAS is I/O bound. The trick is to separate the I/O channels but that may not be your issue w/o more info.
Can you split the jobs so that they are reading from different I/O channels? You indicate no issues on RAM or CPU but that is normally not what slows SAS down.
Too many jobs actually can hurt a system since it will constantly buffer in and out. You are normally better off finding the optimal level vs picking a random number, like 300, and shooting them all at the same time. Do 10, then 50, then 100, so on. Find a balance.
In general, the issue is 'normally' not a system issue but the code logic for what you are trying.
Hip shooting here, just what I have seen.
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