Content cache areas
A content cache area is an area that contains frequently accessed document content that has been duplicated from the original content that resides in storage areas. Typically, a cache delivers content to users who are in the same local area network (LAN) as the cache. The purpose of a cache is to expedite access to the document content of any geographically remote or slow-to-access storage areas.
In Enterprise Manager, you can configure the following cache attributes:
- Storage areas serviced
A cache can be assigned to one of the following owner objects within the server hierarchy (listed from highest to lowest level): site, virtual server, or server instance. This assignment determines the servers that use the cache: a server finds the lowest-level server hierarchy owner to which both the server and a cache belong. For any content not found by the server in the cache, the server copies the content from the storage area into the cache. For information about assigning a cache to a server hierarchy object, see Assign a content cache area. The level of caching permitted for a storage area is set independently of the cache area assignment and is not affected by that assignment. For example, only cross-site caching might be permitted for a storage area. For information about the permitted caching as set by the Content Caching property, see Storage area properties (Configuration tab).
- Content preloading
A cache can automatically load the content of a document upon document checkin. For more information, see Content cache area properties (Processing tab).
- Cache size
A cache can automatically purge content that has not been accessed recently. For more information about the deletion of content from the cache, see the Pruning section in this topic and also Content cache area properties (Processing tab).
Pruning
Pruning is the activity of deleting content files that have not been accessed recently. The purpose of pruning is to ensure that the cache is the minimum size necessary to store the most recently accessed content.
Two types of pruning operations can occur:
- Periodic pruning (triggered by the Content Lifespan property)
Periodic pruning removes content files that have not been accessed for a longer time than the time allowed by the Content Lifespan property. (Document content that is accessed frequently enough can remain in cache indefinitely.) The pruning occurs automatically halfway through the period specified by the Content Lifespan property.
- Mandatory pruning (triggered by the Content Lifespan property)
Mandatory pruning removes content files in least-recently-accessed order until the total number and size of the remaining files does not exceed some calculated target total. The target total calculation involves a property that specifies the percentage to prune and the following threshold properties: Threshold Size and Threshold Elements. The pruning occurs automatically when the number or size of the content files exceeds one of these thresholds.
Content cache area management
IMPORTANT Disable content caching for storage areas that contain confidential or sensitive documents. The deletion of content in a storage area does not delete the copied content in a cache area. Confidential or sensitive content in a cache can remain accessible to users after the deletion of the original content from a storage area.
The following content cache configuration guidelines can help improve your system performance:
- Configure for same site access.
Configure one content cache area to be shared on a high-speed network by servers in the same site within the domain. Avoid locating a content cache area remotely over a slow-speed network.
- Use cache directory for caching.
Do not store documents in a directory designated as a content cache area. Storing other documents in that directory consumes space required for content caching.
- Optimize pruning threshold using the Threshold Size property.
Set the Threshold Size property to optimize system performance. If the content cache server has a large hard disk, you can afford to enlarge the maximum space for content caching. Doing so minimizes network traffic and reduces network access time by keeping the most recently accessed content in local cache. If your caching server has limited space available, reduce the maximum space for content caching. Allocating more space than the server has available can tie up system resources and slow down system performance.
- Optimize pruning threshold using the Threshold Elements property.
Determine the number of files frequently accessed by users. Increase that number by 5-10% to determine the maximum number of files allowed in the cache. If your system maintains relatively small files, you can allow a greater number of files in cache.
- Preload accessed content only.
Do not enable the Preload On Create option when the associated site is heavily used to create documents that are not retrieved later.
- Adjust Content Lifespan property.
Review your system requirements before setting the Content Lifespan interval. The shorter the lifespan is, the more often content is removed and refetched. The longer the lifespan is, the more deleted content occupies the content cache area..
- Periodically review cache properties.
Analyze the content cache settings periodically and modify the configuration properties as necessary. For example, you might experience a system slowdown if users access more files than the configured threshold permits for the content cache area. In this case, increase the maximum number of files allowed.
- Make the cache accessible to servers.
Make
a cache area accessible from every Content Engine server in the FileNet P8 domain. If only some servers have access to the area, the information displayed by Enterprise Manager depends on the server to which Enterprise Manager is connected. No information is displayed for a non-accessible storage area.
A server that does not have access to a cache generates the following error every 30 seconds: CONTENT_CACHE_AREA_ACCESS_FAILED: Access to the content cache area directory failed. This error shows up in the system error logs.