For fast response time to client requests, Directory Server caches directory information in memory. For top performance, you can tune your suffix entry cache settings to optimize performance. Directory Server provides easier control of cache sizing, and once tuned, the server adheres strictly to the cache setting.
This section describes the main features of the Directory Server cache:
Setting thresholds on dynamic memory use
Optimizing cache memory allocation
Grouping entries for simplified management
Directory Server allows you to strictly control the use of memory for cache purposes so that less memory is used. You specify a low and high threshold for dynamic memory use. When this threshold is reached, Directory Server attempts to free memory from the suffix entry caches and to keep memory use under control. If the server reaches the high threshold, the server goes into aggressive mode to free memory. Performance is only effected when the high threshold is reached.
This feature provides two configurable thresholds: a soft threshold and a hard threshold. When the soft threshold is reached, Directory Server attempts to free memory concurrently with other operations. When the hard threshold is reached, operations on the cache are prevented while memory is being freed. These two thresholds are defined by two server properties:
heap-high-threshold-size specifies the hard threshold.
heap-low-threshold-size specifies the soft threshold.
See the server(5dsconf) man page for details on the two server properties.
The size of the cache determines how the memory is allocated. For example, if the cache is less than two Gbytes, the server uses one memory pool. If the cache size is larger than two Gbytes, the server optimizes cache memory allocation by using as many pools as necessary, with each pool dedicated to a particular size.