Starting with Analyst version 11.10, the number of jobs that can be concurrently executed is based on available license features and the job scheduler configuration. For node locked licenses, you are allowed to run on up to 8 cores. By default those cores can be utilized in a variety of ways (e.g. 8 single core jobs, 4 two core jobs, 1 eight core job, etc). Floating licenses are allow to run on up to 8 cores per ANA_300 or 4-TOK_100 license feature. For example, if you have 8 TOK_100 license features available you can run on up to 16 cores.
Note that initial mesh jobs can always run concurrent to other jobs.
In some cases it is desirable to avoid concurrent execution to avoid running out of memory. This can be controlled using the Allow Concurrent Execution parameter on the Job tab of the Simulation Properties dialog box. To access this dialog box, create a simulation, then on the Simulation ribbon in the Settings group, choose Properties.