Databases Reference
In-Depth Information
Real-Time ROLAP Scenario
In the real-time ROLAP scenario, the storage for the partitions and dimensions is set to
ROLAP. The values for properties in this scenario are as follows:
.
SilenceInterval
=
-1
.
SilenceOverrideInterval
= N/A
.
Latency
=
0 sec
.
ForceRebuildInterval
=
-1
(infinite)
The real-time ROLAP scenario enables applications to show the user the latest version of
the data available in the relational database. In the ROLAP mode, Analysis Services keeps
internal caches so that it can improve the performance of similar queries. The data
Analysis Services shows to the user can get out of sync with the data in the relational
database. However, in the real-time ROLAP scenario, Analysis Services drops ROLAP caches
when it receives a change notification because the
Latency
property is set to
0
.
NOTE
If you know that your system behaves different from the settings in one of the scenar-
ios, we recommend that you pick the scenario closest to your requirements and use
the Storage Options dialog box to modify the values of the proactive caching properties.
Change Notifications and Object Processing During
Proactive Caching
Proactive caching, for the most part, is driven by the capability of Analysis Services to
receive notifications about data changes in the relational database. Beyond that, for low-
latency systems, you have to figure out
how
data has changed.
Scheduling Processing and Updates
Internally, Analysis Server keeps a list of DSV (Data Source View)
TableID
values for every
object that has proactive caching enabled. (For information about DSVs, see Chapter 18,
“DSVs and Object Bindings.”) When a notification about a change in the relational table
arrives, Analysis Services flags the DSV
TableID
as changed. Analysis Services uses this
information to determine which objects need to be updated. In the example in Figure
24.5, notifications arrived at
TableID1
and
TableID3
, so the corresponding objects
Dim1
and
Part1
need to be updated.
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