As explained in the SQL Repositories chapter of the ATG Repository Guide, you can set up repository items to have transient attributes, which are readable and writable but are neither stored in nor read from the persistent data store.

For a scenario to access transient profile properties, it must include an event element that establishes a session has begun (for example, a Session Starts or Views event). The event must occur before any subsequent scenario actions that use the transient properties.

Bear in mind also that the scenario can evaluate transient properties as long as the user’s session is active. When the session expires, the Personalization module sets the transient property value to null, and the Scenarios module can no longer use it as a criterion for scenario evaluation.