Bulk Plan Caches

OTM stores in memory, or caches, various data and computed results that are used frequently in a bulk plan. The cached information helps reduce database access and computation times significantly and improve bulk plan performance.

Important statistics on cache usages can be accessed on the Diagnostics and Tools servlet “glog.webserver.cache.CacheDiagServlet”. This servlet provides cache statistics such as size, capacity, timeout, hit ratio, swap ratio, gets, and puts.

The following cache attributes are specific to an LRU (least recently used) type cache, and these can be set through a cache property.

• Capacity: This specifies the size limit of an LRU cache.
• Timeout: This specifies the time limit in seconds after which an item could be removed from an LRU cache.

The following are important performance measures of a cache.

• Size: Number of elements currently in the cache.
• Gets: Total number of items requested from the cache.
• Puts: Total number of items put into the cache.
• Hit Ratio: Ratio of cache Hits to cache Gets.
• Swap Ratio: Ratio of cache Swaps to cache Gets.

A Hit occurs if a requested item is already in the cache. A Hit Ratio of 1.0 is ideal. If the cache is full (i.e. size = capacity), and hit ratio is not very high (less than 0.95), this means that current cache capacity is not sufficient. In this case, bulk plan runtime performance can be further improved by increasing the capacity of these caches. The following properties are available to provide cache performance related warnings during a bulk plan.

• glog.bulkplan.warning.minimumGetsForWarning
• glog.bulkplan.warning.minimumHitRatio
• glog.bulkplan.warning.turnOnCacheChecking

When the "glog.bulkplan.warning.turnOnCacheChecking" property is on, OTM will warn about caches with low hit ratio in the Bulk Plan Performance tab, but only for certain caches: TItemCache, TLocation, TRateOfferingCache, TRateGeoCache, TPackagedItemCache, TSpecialServiceCache, TEquipmentGroupCache.