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VMS Help SUBMIT, Qualifiers, /AFTER *Conan The Librarian |
/AFTER=time
/NOAFTER
Requests that the job be held until after a specific time. If
the specified time has passed already, the job is processed
immediately.
You can specify time as either absolute time or as a combination
of absolute and delta times. For complete information on
specifying time values, see the OpenVMS User's Manual or the
online help topic Date.
In an OpenVMS Cluster, a batch job submitted to execute at a
specific time may begin execution a little before or after the
requested time. This occurs when the clocks of the member systems
in the OpenVMS Cluster are not synchronized. For example, a job
submitted using the DCL command SUBMIT/AFTER=TOMORROW may execute
at 11:58 P.M. relative to the host system's clock.
This problem can occur in a cluster even if a job is run on
the same machine from which it was submitted, because the
redundancy built into the batch/print system allows more than
one job controller in the cluster to receive a timer asynchronous
system trap (AST) for the job and, thus, to schedule it for
execution. Moreover, this behavior is exacerbated if the batch
job immediately resubmits itself to run the next day using the
same SUBMIT command. This can result in having multiple instances
of the job executing simultaneously because TOMORROW (after
midnight) might be only a minute or two in the future.
A solution to this problem is to place the SUBMIT command in
a command procedure that begins with a WAIT command, where
the delta-time specified in the WAIT command is greater than
the maximum difference in time between any two systems in the
cluster. Use the SHOW TIME command on each system to determine
this difference in time. Use the SYSMAN command CONFIGURATION
SET TIME to synchronize clocks on the cluster. For complete
information on the SYSMAN command CONFIGURATION SET TIME, see
the HP OpenVMS System Management Utilities Reference Manual.
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