Oracle Forms Developer – Form Builder Reference, Volume 1

SYSTEM.DATE_THRESHOLD system variable
Syntax
SYSTEM.DATE_THRESHOLD
Description
SYSTEM.DATE_THRESHOLD represents the database date requery threshold. This variable works in
conjunction with the three system variables $$DBDATE$$, $$DBDATETIME$$, and $$DBTIME$$,
and controls how often Form Builder synchronizes the database date with the RDBMS. The value of this
variable must be specified in the following format:
MI:SS
Because frequent RDBMS queries can degrade performance, it is best to keep this value reasonably high.
However, keep in mind that if the value is not synchronized often enough, some time discrepancy can
occur. In addition, if you are building a client/server application, the performance implications of
SYSTEM.DATE_THRESHOLD could vary depending on the complexity of your network
configuration.
Default
01:00 (Synchronization occurs after one minute of elapsed time.)
This does not mean that Form Builder polls the RDBMS once every minute. It means that whenever
Form Builder needs to generate the value for the system variables $$DBDATE$$, $$DBDATETIME$$,
$$DBTIME$$, or SYSTEM.EFFECTIVE_DATE, it updates the effective date by adding the amount of
elapsed time (as measured by the local operating system) to the most previously queried RDBMS value.
If the amount of elapsed time exceeds the date threshold, then a new query is executed to retrieve the
RDBMS time and the elapsed counter is reset.
Usage Notes
If a form never references the database date, Form Builder never executes a query to retrieve the
RDBMS date, regardless of the value of SYSTEM.DATE_THRESHOLD.
The operating system clock and the RDBMS clock rarely drift by more than one or two seconds, even
after hours of elapsed time. However, since your database administrator can reset the RDBMS clock at
any time, it is safest to set the threshold no higher than a few minutes.
Often, a Form Builder block may contain multiple references to these $$DBDATE$$,
$$DBDATETIME$$, or $$DBTIME$$ defaults. By setting SYSTEM.DATE_THRESHOLD to the
default of one minute, nearly all such references in a form can be satisfied with a single query of the
RDBMS.
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