Automatically purge versions of metadata documents older than the given time interval.

It is mentioned properly in the following document

6.3 Purging Document Version History

http://download.oracle.com/docs/cd/E14571_01/core.1111/e10108/mds.htm#BEIFIBEF

Automatic purge can be performed in two ways

1>Add the following to your adf-config.xml and then deploy it to your project

<persistence-config>
<auto-purge seconds-to-live="T"/>
</persistence-config>


You can get the adf-config.xml in your jdeveloper as shown below.
Here time out is in seconds




You can also set the same from em console also

Log in to your em console

http://host:port/em

Go to Soa-infra-->Administration-->System MBean Browser

as shown below



Now Navigate to following path

Application Defined MBeans-->oracle.adf.share.config-->Server:AdminServer

-->Application:sos-infra-->ADFConfig-->MDSAppConfig as shown below

Here you can see a property called as AutoPurgeTimeToLive

you can set the value as per your requirement and it will have same result

as the changes done in adf-config.xml