About Refresh Dates
1) Refresh dates refer to the date of the last ETL process (the last time data was extracted from tables in a given database or loaded into tables in a given database).
2) DAC uses the refresh dates to determine whether to run the incremental load commands or to run full load commands and whether to truncate the target tables.
3) Refresh dates are tracked only for tables that are either a primary source or a primary target on tasks in a completed run of an execution plan.
4) DAC runs the full load command for tasks on which a table is a primary source or target if the refresh date against the table is null.
5) When there are multiple primary sources, the earliest of the refresh dates will trigger a full load or an incremental load.
6) If any one of the primary source tables has no refresh date, then DAC will run the full load command.
Table 9–1 shows the possible scenarios regarding refresh dates.
Scenario Table Type (in Tasks child tabs) Refresh Date Command DAC
Will Use Truncate Target Table?
1 Primary Source Null Full Load Yes
1 Primary Target Null Not applicable Not applicable
2 (See note
Primary Source Null Full Load No
2 Primary Target Not Null Not applicable Not applicable
Primary Source Not Null Full Load Yes
3 Primary Target Null Not applicable Not applicable
4 Primary Source Not Null Incremental
4 Primary Target Not Null Not applicable Not applicable
■ Scenario 2. When two or more source tables load into the same target table as
separate tasks, the source table in the second task may have refresh date as null
while the target may have a refresh date.
■ Scenario 3. When a source loads into more than one target table in separate tasks,
the refresh date may be null for the second target table while the source table may
have refresh dates.