By default, each Orchestrator Runbook Server is configured to simultaneously run a maximum of 50 runbooks. This is to control the CPU and Memory load placed on the Orchestrator Runbook Server by executing Runbooks.
You can change this number by using the Runbook Server Runbook Throttling tool. In most cases, you can increase the default setting. If Orchestrator has a number of Runbooks with high CPU or Memory resource requirements, you might run fewer Runbooks simultaneously.
Normal Runbooks have minimal requirements and execute very quickly and therefore place a very small load on the Runbook Server CPU and Memory. In fact queueing up Runbooks, because of the maximum simultaneous Runbook limit has been reached, actually excesses the CPU and Memory load on the Runbook Server because each queued Runbook takes up Memory space whilst it waits to be executed.