Setting an operation cache policy for mobile business object (MBO)
operations gives you more control of SAP Mobile Server interactions with the enterprise
information system (EIS) to which the MBO is bound, and SAP Mobile Server cache (CDB) updates.
Fine-tuning these interactions and updates improves both SAP Mobile Server and device
application performance.
MBO operations perform specific functions based on their definition:
- Read operation (MBO attributes, load arguments, and synchronization parameters)
– the EIS operation used to define and initially populate the CDB (from the EIS)
for the MBO. Also called a load operation.
- Create, Update, Delete (CUD operations) – modify EIS data depending on the
definition of the operation. SAP Mobile Server maintains a cache (CDB) of back-end
EIS data to provide differential synchronization and to minimize EIS
interaction.
While this type of bulk-fetch and CDB caching are effective in
reducing the number of interactions required with the EIS, and work well in
some other cases (where MBO data is occasionally updated in the EIS),
performance suffers if changes are initiated from SAP Mobile Server (by way of
MBO operations), or if changes are frequent.
When an operation is
submitted from a device application to the EIS, the cache must be refreshed
for those changes to be available to a client the next time the client
synchronizes.
- Entity Read operations – refresh a single instance of an MBO composite graph
(MBOs in a composite relationship) in the SAP Mobile Server cache (CDB). This type
of operation can only be invoked for Create and Update operations that use an
"Immediately update the cache" operation cache policy.
Operation cache policies determine how the CDB is updated after an
operation executes. The operation cache policy and option combinations from which to
choose to associate with MBO CUD operations include:
- Immediately update the cache with Apply merge of operation
input/output
- (Legacy) Apply results to the cache
- Immediately update the cache with Apply output of ENTITY READ
operation
- Invalidate the cache
- None
When an MBO operation is called, its cache policy determines how operation results are
applied to the CDB.
Other mechanisms used to update the CDB that are external to MBO operations, and not
associated with operation cache policies include:
- EIS-initiated DCN – an HTTP request to SAP Mobile Server, in which the DCN request
contains information about the changed data, or the changed data itself.
- Scheduled data refresh – SAP Mobile Server polls the EIS for changes at specified
intervals.
- MBO cache group – every MBO belongs to a cache group that specifies a cache
refresh policy for every MBO in that group. Plan carefully to maximize cache
group and cache policy efficiency. Examples include:
- A poorly designed MBO might have an operation with a cache policy that
updates only the operation results to the CDB, but the MBO belongs to a
cache group with an interval that refreshes the entire MBO on too short
a schedule, minimizing the value of the cache policy.
- This same MBO properly designed might have a cache group that refreshes
the MBO nightly, increasing SAP Mobile Server performance by deferring load
from peak usage hours.