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

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 the cache holds.

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

Default priority

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

Whether disk offload is enabled.

By default, the dynamic cache maintains the number of entries 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

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 will be 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 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.

• 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

Enable cache replication

Use cache replication to have cache entries copied to multiple application servers that are configured in the same replication domain.

Full group replication domain

Specifies a replication domain from which your data is replicated.

Choose from any replication domains that have been defined. If there are no replication domains listed, create one during cluster creation or manually in the administrative console by clicking Environment > Internal replication domains > New. The replication domain you choose to use with the dynamic cache service must be using a Full group replica. Do not share replication domains between replication consumers. Dynamic cache should use a different replication domain from session manager or stateful session beans.

Replication type

The global sharing policy for this application server. The following settings are available:

• Both push and pull sends the cache ID of newly updated content to other servers in the replication domain. Then, if one of the other servers requests the content, and that server has the ID of the cache entry for the previously updated content, it will retrieve the content from the publishing server. On the other hand, if a request is made for an ID which has not been previously published, the server assumes it does not exist in the cluster and creates a new entry.

• Push only sends the cache ID and cache content of new content to all other servers in the replication domain.

• The sharing policy of Not Shared results in the cache ID and cache content not being shared with other servers in the replication domain.

The default is Not Shared.

Push frequency

The time, in seconds, to wait before pushing new or modified cache entries to other servers.

A value of 0 (zero) sends the cache entries immediately. Setting this property to a value greater than 0 (zero) results in a "batch" push of all cache entries that are created or modified during the time period. The default is 1 (one).

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