PowerExchange ODBC uses the restart tokens associated with application names in the CDEP file to determine the starting extraction point for a session. The CDEP file used is the one maintained by PowerExchange on the platform targeted by the extraction. The CDEP file contains both begin and end restart tokens for each extraction. This differs from PWXPC where only the end restart tokens are maintained in the restart token file.

The restart tokens determine the baseline point from which to extract the change data for the source database. Since both start and end restart tokens are available when you use ODBC, the extraction type decides which ones will be used for restart. The extraction type is specified in the ODBC connection in the CAPXTYPE parameter. This can be overridden at the session level by using the SQL Escape Sequence DTLXTYPE.

If the extraction type specified is Since Last (SL) then the extraction will commence at the last successful ending point. If it is Restart (RS) then it will commence at the starting point of either the last successful extraction that was run or the one that is specified with the Reset Start Point in the extraction application dialog box in the PowerExchange Navigator.

The CDEP information for an extraction is only updated when a session ends successfully. Failed sessions do not update the restart token information in the CDEP with the progress so far.