Optimization of Submission Time
condor_dagman works by watching log files for events, such as submission, termination, and going on hold. When a new job is ready to be run, it is submitted to the condor_schedd, which needs to acquire a computing resource. Acquisition requires the condor_schedd to contact the central manager and get a claim on a machine, and this claim cycle can take many minutes.
Configuration variable DAGMAN_HOLD_CLAIM_TIME avoids the wait for a negotiation cycle. When set to a non zero value, the condor_schedd keeps a claim idle, such that the condor_startd delays in shifting from the Claimed to the Preempting state (see Configuration for Execution Points). Thus, if another job appears that is suitable for the claimed resource, then the condor_schedd will submit the job directly to the condor_startd, avoiding the wait and overhead of a negotiation cycle. This results in a speed up of job completion, especially for linear DAGs in pools that have lengthy negotiation cycle times.
By default, DAGMAN_HOLD_CLAIM_TIME is 20, causing a claim to remain
idle for 20 seconds, during which time a new job can be submitted
directly to the already-claimed condor_startd. A value of 0 means
that claims are not held idle for a running DAG. If a DAG node has no
children, the value of DAGMAN_HOLD_CLAIM_TIME will be ignored; the
KeepClaimIdle attribute will not be defined in the job ClassAd of
the node job, unless the job requests it using the submit command