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6.8 Setting custom system properties
Important: You should use the administrative console to set the following three custom properties in V6.1. Setting them manually is not recommended.
Disk cache cleanup
You can activate the disk cache cleanup once a day at a specified time by using the com.ibm.ws.cache.CacheConfig.htodCleanupHour system property. In the Administrative Console:
1. Select Application servers Æ <your server> Æ Process Definition Æ Java Virtual Machine Æ custom properties
2. Click the New button and declare the system property as the key and its value in the value field, which defaults to 0 (= 12:00 midnight). Or you can specify the cleanup to run at a specific frequency by setting the com.ibm.ws.cacheCacheConfig.htodCleanupFrequency system property. Its value is expressed in minutes. The disk cache cleanup occurs in two phases: scan and delete. In the scan phase, the algorithm identifies objects that have expired on disk. Since the cleanup algorithm is only looking for expired entries, cached objects without an expiration value (an expiration value of 0) will always remain on disk until explicitly invalidated.
The policy of never expiring objects should be reconsidered if disk space is an issue in the deployment. The delete phase returns disk space to the internal storage manager and ensures that all references to the object are correctly purged. Most large deployments that have a large amount of content on the disk typically choose to specify that cleanup occurs at a frequency that ranges from 30 minutes to a couple of hours, depending on the average expiration time of content in the cache.
You can optimize the disk cache cleanup for disk I/O by buffering the metadata that is associated with cached objects in memory. These auxiliary buffers can hold the dependency and template information for the objects so that the object deletion time is decreased.