Custom JVM properties
There are three custom properties available:
| 1. | htodCleanupFrequency |
| 2. | htodDelayOffloadEntriesLimit |
| 3. | htodDelayOffload |
The first, htodCleanupFrequency, is related to the disk cache cleanup time The other two properties, described in the following sections, are related to tuning the delay offload function.
htodCleanupFrequency
Tune the disk cache cleanup time using the com.ibm.ws.cache.CacheConfig. htodCleanupFrequency custom property. This property defines the amount of time between disk cache cleanups. By default, the disk cache cleanup is scheduled to run at midnight to remove expired cache entries and cache entries that have not been accessed in the past 24 hours. However, if you have thousands of cache entries that might expire within one or two hours, the files that are in the disk cache can grow large and become unmanageable.
Use com.ibm.ws.cache.CacheConfig.htodCleanupFrequency to change the time interval between disk cache cleanups. The value is set in minutes, that is, a value of 60 means 60 minutes between each disk cache cleanup. The default is 0 which means that the disk cache cleanup occurs at midnight every 24 hours.
| Tip: If you are using objects that use inactivity or timeout to clean up, then configure this parameter to execute more frequently. If you use a 15 minute timeout we suggest you use a 15 minute cleanup interval. |
htodDelayOffloadEntriesLimit and htodDelayOffload
Tune the delay offload function using these custom properties:
| com.ibm.ws.cache.CacheConfig. htodDelayOffloadEntriesLimit |
|
| com.ibm.ws.cache.CacheConfig. htodDelayOffload |
The delay offload function uses extra memory buffers for dependency IDs and templates to delay the disk offload and minimize the input and output operations. However, if most of your cache IDs are longer than 100 bytes, the delay offload function might use too much memory.
To increase or decrease the in-memory limit, use com.ibm.ws.cache.CacheConfig.htodDelayOffloadEntriesLimit. This custom property specifies the number of different cache IDs that can be saved in memory for the dependency ID and template buffers. Consider increasing this value if you have a lot of memory in your server and you want to increase the performance of your disk cache. The default value in WebSphere Commerce is 100,000,1 which means that each dependency ID or template ID can have up to 100,000 different cache IDs in memory. Specify a value suitable for your environment, but it must be a number higher than 100 because this is the minimum setting allowed.
The com.ibm.ws.cache.CacheConfig.htodDelayOffloadcustom property specifies whether extra memory buffers are used in memory for dependency IDs and templates to delay disk offload and to minimize input and output operations to the disk. The default value is true, which means enabled. With the property enabled, there is a considerable performance boost in disk cache throughput. Consider disabling it if your cache IDs are larger than 100 bytes because this option might use too much memory when it buffers your data. If you set this property to false, all the cache entries are copied to disk immediately after they are removed from the memory cache.
1WebSphere Commerce already modifies the WebSphere Application Server from its default of 1000.