Servlet cache instance settings

A servlet cache instance is a location, in addition to the default shared dynamic cache, where dynamic cache can store, distribute, and share data. By using servlet cache instances, your applications have greater flexibility and better tuning of the cache resources. The Java Naming and Directory Interface (JNDI) name specified for the cache instance is mapped to the name attribute in the <cache-instance> tag in the cachespec.xml configuration file.

To view this administrative console page, click Resources > Cache instances > Servlet cache instances > cache_instance_name.

Name

The required display name for the resource.

JNDI name

The Java Naming and Directory Interface (JNDI) name for the resource. Specify this name in the name attribute field in the <cache-instance> tag in the cachespec.xml configuration file. This tag is used to find the particular cache instance in which to store cache entries.

Description

Specifies a description for the resource. This field is optional.

Category

Specifies a category string to classify or group the resource. This field is optional.

Cache size

Specifies a positive integer for the maximum number of entries the cache holds. The cache size is usually in the thousands.

Default	2000
Range	100 - no set maximum value

Default priority

The default priority for servlets that can be cached. This value determines how long an entry stays in a full cache.

The recommended value is one.

Enable disk offload

Specifies if disk offloading is enabled.

If you have disk offload disabled, when a new entry is created while the cache is full, the priorities are configured for each entry and the least recently used algorithm are used to remove the entry from the cache in memory. If you enable disk offload, the entry that would be removed from the cache is copied to the local file system. The location of the file is specified by the disk offload location.

Default

false

Offload location

The directory used for disk offload.

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

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 enable sharing of cache IDs, cache entries, and cache invalidations with other servers in the same replication domain.

This option might be unavailable for cache instances created with a previous version of WebSphere Application Server.

Full group replication domain

Specifies a replication domain from which your data is replicated.

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 cache instance. 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. 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.

• Pull only shares cache entries for this object between application servers on demand. If an application server gets a cache miss for this object, it queries the cooperating application servers to see if they have the object. If no application server has a cached copy of the object, the original application server runs the request and generates the object. These entries cannot store non-serializable data. This mode of sharing is not recommended.

• 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 setting for a an environment without clustering is Not Shared. When enabling replication, the default value 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).

Related tasks

Related reference
Object cache instance collection Object cache instance settings Servlet cache instance collection