Nirvana RTD : Channel Configuration

Due to the way the Nirvana RTD server handles sessions (see RTD Sessions), it may seem that the specified channel configuration is not being honoured.

Nirvana does not allow one user to be subcribed to a channel more than once within one session. This leads to the following situations:

User allready subscribed error

Sessions are created based on the RNAME field. If two cells try to subscribe to the same channel within the same session but specify different channel configurations then this error message will be shown.

In this situation, the Nirvana RTD server will attempt to create a new subscription to the channel but with different parameters for example a different start eid. This is not possible within Nirvana.

If you require two subscriptions with different configurations then you should specify a different value in the RNAME field which will cause the Nirvana RTD server to create a new session. Specifying a different value for the RNAME field does not mean specifying a new realm. You can make this field distinct by using the same realm but with a different user name.

Cell not subscribing from correct eid

Once a cell has been initialised to subscribe to a channel from a particular eid (0 for example), the RTD server will immediately begin to consume events and return the required data to the cell. This means that if another cell is initialised for the same channel and eid a few moments later, that cell will not receive all the events from that eid onward as the subscription is shared with the first cell which has already consumed some events.

By restarting Excel, both cells will connect before any events are processed and therefore both cells will receive the required data.

Alternatively you may create a new session for that realm and therefore a new subscription. To do this a different value must be given in the RNAME field by using a different user name for example.