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Oracle TopLink Developer's Guide 10g Release 3 (10.1.3) B13593-01 |
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# Historical Client Session Configuration Overview

There are two ways to configure TopLink to access the historical versions of objects maintained by your data source:

- Configuring Historical Client Sessions Using an Oracle Platform

- Configuring Historical Client Sessions Using a TopLink HistoryPolicy

## Configuring Historical Client Sessions Using an Oracle Platform

Oracle9i Database Server (or later) automatically maintains historical versions of objects and extends SQL with an `AS_OF` clause used to query this historical data. Oracle refers to these as flashback queries.

If you configure your `Session` with an `OraclePlatform` (see "Configuring a Relational Database Platform at the Session Level") for Oracle9i Database Server (or later), you can query the historical versions of objects automatically maintained by Oracle Database.

No further session configuration is required.

For more information, see the following:

- "Acquiring a Historical Client Session"

- "Historical Queries".

## Configuring Historical Client Sessions Using a TopLink HistoryPolicy

If you configure your `Session` with a non-Oracle platform (see "Configuring a Relational Database Platform at the Session Level") using a schema you design to maintain historical versions of objects and if that schema can be described by TopLink `HistoryPolicy`, you can query the historical versions of objects maintained by your database in accordance with your schema.

For more information, see the following:

- "Configuring a History Policy"

- "Acquiring a Historical Client Session"

- "Historical Queries".