To prevent too many queued executions from overwhelming a Domino deployment, the number of execution slots that can be queued globally or per user can be limited. To do this, please reach out to Domino Support.
Once a queue limit is reached, additional executions are rejected with a failure status. The count includes executions for Domino workspaces, jobs, web applications, and any executions that make up an on-demand distributed compute cluster. For example, an on-demand Spark cluster consumes an execution slot for the master and each Spark executor.