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4.6.9 Troubleshooting Geographical Replication
In addition to using the ReplicaRuntimeMBean methods described in Section 4.6.8,
Monitoring Replication Across Regional Sites , Administrators should monitor any
SNMP traps that indicate failed database writes on a secondary site installation. Administrators must also ensure that all sites participating in
geographically-redundant configurations use unique site IDs.
4.7 Caching SIP Data in the Engine Tier
As described in Chapter 7, Oracle WebLogic Server SIP Container Base Platform
Topologies , in the default Oracle WebLogic Server SIP Container configuration the
engine tier cluster is stateless. A separate SIP data tier cluster manages call state data in one or more partitions, and engine tier servers fetch and write data in the SIP data
tier as necessary. Engines can write call state data to multiple replicas in each partition to provide automatic failover should a SIP data tier replica going offline.
Oracle WebLogic Server SIP Container also provides the option for engine tier servers to cache a portion of the call state data locally, as well as in the SIP data tier. When a
local cache is used, an engine tier server first checks its local cache for existing call state data. If the cache contains the required data, and the local copy of the data is
up-to-date compared to the SIP data tier copy, the engine locks the call state in the SIP data tier but reads directly from its cache. This improves response time
performance for the request, because the engine does not have to retrieve the call state data from a SIP data tier server.
The engine tier cache stores only the call state data that has been most recently used by engine tier servers. Call state data is moved into an engines local cache as necessary in
order to respond to client requests or to refresh out-of-date data. If the cache is full when a new call state must be written to the cache, the least-recently accessed call state
entry is first removed from the cache. The size of the engine tier cache is not configurable.
Using a local cache is most beneficial when a SIP-aware load balancer manages requests to the engine tier cluster. With a SIP-aware load balancer, all of the requests
for an established call are directed to the same engine tier server, which improves the effectiveness of the cache. If you do not use a SIP-aware load balancer, the
effectiveness of the cache is limited, because subsequent requests for the same call may be distributed to different engine tier severs having different cache contents.
4.7.1 Configuring Engine Tier Caching
Engine tier caching is enabled by default. To disable partial caching of call state data in the engine tier, specify the engine-call-state-cache-enabled element in
sipserver.xml:
engine-call-state-cache-enabledfalseengine-call-state-cache-enabled When enabled, the cache size is fixed at a maximum of 250 call states. The size of the
engine tier cache is not configurable.
4.7.2 Monitoring and Tuning Cache Performance
SipPerformanceRuntime monitors the behavior of the engine tier cache. Table 4–3
describes the MBean attributes.
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