Kal,

The snapshot kept by Lightstreamer Server for an item is cleared only when no more clients are subscribed to that item.

If snapshot management is not needed at all, then RAW mode could be used instead of COMMAND mode. On the other hand, if snapshot management is required, when a Data Adapter fails, it has two options: a) manage the data recovery, by sending the necessary updates to LS Server to keep a coherent snaoshot; b) call a failure to make the LS Server restart.

Lightstreamer Server 4.0 (not available soon) will feature complete item status management, with the possibility of marking individual items as stale and letting the system handle coherency.

In the meanwhile, some workarounds could be implemented with the client collaboration. For example, for each COMMAND-mode item, a status item could be associated. If the feeder for the COMMAND-mode item fails, it pushes a notification through the status item. As a consequence, the client will unsubscribe from the COMMAND-mode item and will resubscribe to it with a new name (e.g. appending an incremental number to the item name). This will provoke the unsubscription to the stale item, and the snapshot flush. At the same time, the Adapter will start serving that item from scratch under a different name.