Recording of Historical Data
The system can maintain historical parcel boundary and alphanumerical data indefinitely. Production of a complete audit trail for changes to attribute data and land parcel boundaries is also
supported.
Depending on the requirements, there are a few options available. The default option is to audit every transaction and to keep history on every update on geometries. For this we use two separate
Oracle tables. The audit table has a fixed structure and includes information like who, what, when while the history table has the same structure as the original table plus a column for storing the
date when the geometry went to history. All those dates are managed by transactions i.e. when a user changes a border between two (or more) polygons the data are all moved into history with the
same date. From such a history table every step can be traced back, but in environments where many updates are expected, the table can grow very fast. In this case a different backup option can be
used or the table can be periodically cleaned.
In case intermediate steps are not important the scenario with history updates at the end can be used whereby the application just ignores history records and fills in history info when the user
finishes the update process.
references