Cache Update Policy

Fine-tune device application and Unwired Server performance by defining a cache update policy for mobile business object operations.

Setting a cache update policy for mobile business object (MBO) operations gives you more control of both Unwired Server interactions with the enterprise information system (EIS) to which the MBO is bound, and consolidated database updates. Fine-tuning these interactions and updates improves both Unwired Server and device application performance.

Note: Consolidated database, CDB, and cache all refer to the same thing, and the terms are used interchangeably.

MBO operations perform specific functions based on their definition:
- Primary read operation – the EIS operation used to define and initially populate the CDB (from the EIS) for the MBO.
- Create, update, delete (CUD operations) – modify EIS data depending on the definition of the operation. Unwired Server maintains a cache (CDB) of back-end EIS data to provide differential synchronization and to minimize EIS interaction. When an operation is submitted from a device application to the EIS, the cache must be refreshed.
  While these types of bulk-fetch and CDB caching are effective in reducing the number of interactions required with the back-end EIS, and work well in some other cases (where MBO data is occasionally updated in the back-end), performance suffers if changes are initiated from Unwired Server (by way of MBO operations), or if changes are frequent.
  
  The cache update policy introduces alternative methods of updating the cache at finer granularity, which improves performance.
- Alternate read operations – can be invoked either from:
  - A chained read cache policy to augment CUD operations by chaining an alternate read operation to a CUD operation.
  - A data change notification, which provides a mechanism to invoke MBO operations, including alternate read operations. This mechanism is independent of a cache update policy.
Cache update policy – determines how the CDB is updated after an operation. You can set the cache update policy for operations, with these exceptions:
- Operations defined as "Other" do not support alternate read or a cache update policy.
- When invoked, alternate read operations always use the apply operation results cache update policy.
Versions of Sybase Unwired Platform earlier than 1.2.1 supported only the invalidate cache policy—any CUD or other operation issued from a device application invalidated the cache and required a primary read operation to refresh the cache.
In Unwired Platform version 1.2.1, these are the five cache update policies you can associate with MBO CUD operations:
- Invalidate cache
- No invalidate cache
- Apply operation result
- Apply operation parameters
- Chained read
When an MBO CUD operation is called, its cache update policy determines how operation results are applied to the consolidated database. Generally, there are two ways of calling an MBO operation:
1. Device client calls the operation.
2. A data change notification (DCN) request contains the operation.

Note: Other methods used to update the CDBs that are external to MBO operations, and not associated with cache update policies include:

EIS-initiated DCN – an HTTP request to Unwired Server, in which the DCN request contains the payload (information about the changed data).
Note: EIS-initiated DCN also supports HTTP POST requests which provides a higher level of security.
Scheduled data refresh – defined in Sybase Control Center; polls the EIS for changes at specified intervals.