On Demand Cache Refreshes

Cache groups designated as "on demand" during development use cache intervals to balance how frequently the object updates enterprise data with the amount of network traffic required to maintain that data.

SAP Mobile Server keeps a local copy of enterprise data in the cache database (CDB), and uses an intricate mechanism to manage updates between the CDB and the EIS servers. When data is updated, the remote client database eventually gets updated data from this local copy in the CDB. The caching mechanism allows MBOs to retrieve updated data even if back-end servers fail.

You must choose an appropriate cache interval for your system, since this value determines how frequently the CDB is udpated with data from the EIS. The cache interval must be configured according to business needs. A higher value for the cache may retain stale data, however, a lower value increases the backend EIS load and may impede the client application's performance, because SAP Mobile Server queries the back-end information servers more frequently to look for changes and possibly update the CDB copy.

Frequent queries typically put a higher load on the servers, as well as use more network bandwidth on the server side. While the cache interval does not affect the bandwidth required between the synchronization server and device client applications, nor the performance characteristics of the client applications, the interval you choose can delay synchronization if SAP Mobile Server must first update many records in the CDB.

For example, if the cache interval is 0, each time a client application synchronizes, there is a pause while the SAP Mobile Server rereads data from the EIS and updates the CDB. If, however, the cache interval is greater than 0, then the wait time depends on how long ago the data was refreshed. If the synchronization falls within a recent cache update, synchronization is almost immediate.