Dynamic cache service settings

Use this page to configure and manage the dynamic cache service settings.

To view this administrative console page, click Servers > Application servers > server_name > Container services > Dynamic cache service.

Configuration tab

Enable service at server startup

Specifies whether the dynamic cache is enabled when the server starts.

Cache size

Specifies a positive integer as the value for the maximum number of entries that the cache holds.

Enter a cache size value in this field that is between the range of 100 through 200,000.

Default priority

Specifies the default priority for cache entries, determining how long an entry stays in a full cache.

Default 1
Range 1 to 255

Enable disk offload

Specifies whether disk offload is enabled.

By default, the dynamic cache maintains the number of entries that are configured in memory. If new entries are created while the cache is full, the priorities that are configured for each cache entry, and a least recently used algorithm, are used to remove entries from the cache. In addition to having a cache entry removed from memory when the cache is full, you can enable disk offload to have a cache entry copied to the file system (the location is configurable). Later, if that cache entry is needed, it is moved back to memory from the file system.

Before you enable disk offload, consider the following:
  • You cannot specify the number of cache entries that are offloaded to disk.
  • You cannot specify the amount of disk space to use.

Offload location

Specifies the location on the disk to save cache entries when disk offload is enabled.

If disk offload location is not specified, the default location, ${WAS_TEMP_DIR}/node/server name/_dynacache/cache JNDI name is used. If disk offload location is specified, the node, server name, and cache instance name are appended. For example, ${USER_INSTALL_ROOT}/diskoffload generates the location as ${USER_INSTALL_ROOT}/diskoffload/node/server name/cache JNDI name. This value is ignored if disk offload is not enabled.

The default value of the ${WAS_TEMP_DIR} property is ${USER_INSTALL_ROOT}/temp. If you change the value of the ${WAS_TEMP_DIR} property after starting WebSphere Application Server, but do not move the disk cache contents to the new location:
  • The application server creates a new disk cache file at the new disk offload location.
  • If the Flush to disk setting is enabled, all of the disk cache content at the old location is lost when you restart the application server
When you are specifying a directory, consider the following:
  • If you expect to cache a large number of objects or large objects that will be around for some time, consider using a separate disk drive if you are using Windows operating systems, or a separate file system if you are using UNIX platforms.
  • If you use the default directory and the disk fills up, WebSphere Application Server could possibly stall if it needs to write messages to log files, and there is no more space.
  • [AIX] [HP-UX] [Linux] [Solaris] If you specify a directory such as /tmp on UNIX platforms and that directory fills up, you may have trouble logging onto the system.
  • Depending on the operating system, you may see disk full messages on the console.

Flush to disk

Specifies if in-memory cached objects are saved to disk when the server is stopped. This value is ignored if Enable disk offload is not selected.

Default false



Related tasks
Task overview: Using the dynamic cache service to improve performance
Related reference
cachespec.xml file
Reference topic    

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Last updated: Aug 29, 2010 6:22:59 PM CDT
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