Improvements to SCV Purge Planning Table program

The SCV program PURGE_PLANNING_DATA is extended to allow purging data by date. The program now accepts these new parameters:

• DATE_COLUMN (optional): Optional parameter. Name of the column that holds the reference date to purge older data. If specified, the column must exist in all tables in scope.
• DAYS_TO_KEEP (optional): The number of days old data to purge. If specified, the DATE_COLUMN parameter must also be specified.

When the DATE_COLUMN and DAYS_TO_KEEP parameters are specified, the purge program determines the maximum date value available in the specified DATE_COLUMN and deletes all records that are older than the existing maximum date value minus the specified DAYS_TO_KEEP.