Concurrency Limits for each queue

concurrency_limits = <string-list>

    A list of resources that this job needs. The resources are presumed to have concurrency limits placed upon them, thereby limiting the number of concurrent jobs in execution which need the named resource. Commas and space characters delimit the items in the list. Each item in the list is a string that identifies the limit, or it is a ClassAd expression that evaluates to a string, and it is evaluated in the context of machine ClassAd being considered as a match. Each item in the list also may specify a numerical value identifying the integer number of resources required for the job. The syntax follows the resource name by a colon character (:) and the numerical value. Details on concurrency limits are in the HTCondor Administrator’s manual.
concurrency_limits_expr = <ClassAd String Expression>

    A ClassAd expression that represents the list of resources that this job needs after evaluation. The ClassAd expression may specify machine ClassAd attributes that are evaluated against a matched machine. After evaluation, the list sets concurrency_limits.

CONCURRENCY_LIMIT_DEFAULT

    An integer value that describes the number of resources available for any resources that are not explicitly named defined with the configuration variable <NAME>_LIMIT. If not defined, no limits are set for resources not explicitly identified using <NAME>_LIMIT.
CONCURRENCY_LIMIT_DEFAULT_<NAME>

    If set, this defines a default concurrency limit for all resources that start with <NAME>.

(Special user group with special concurrency limits just for them possibly)
Ensure that passed clientgroup is valid
Ensure that bigmem, extreme have a concurrency limit (e.g. of 5)
Ensure that other queues use the concurrency limit of default
Ensure that this is documented somewhere

kbase / execution_engine2

Concurrency Limits for each queue #445