A content cache area contains frequently accessed document
content that was 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.
If the original content is encrypted, the cache copy of that content
is also encrypted. (The original content might be encrypted if you
enabled content encryption for the storage area.)
In the administration console, you can configure the following
cache attributes:
- Content cache area assignment
- A content cache can be assigned to one of the following owner
objects within the site hierarchy (listed from highest to lowest level):
domain, site, virtual server, or server instance. For best results,
assign a content cache area to a site. The assignment determines the
servers that use the cache: a server finds the lowest-level site hierarchy
owner that both the server and a cache belong. For more information
about assigning a cache to a site hierarchy object, see Assigning a content cache area.
- Storage areas that are serviced
- The level of caching permitted for a storage area is set independently
of the cache area assignment and is not affected by that assignment.
The storage area configuration has a property for content caching
that can have one of the following values:
- Not Allowed
- Content from this storage area is never cached in a cache area.
- Cross site only
- Content from this storage area is cached only in content cache
areas that are assigned to a site that is different from the storage
area site.
- Allowed
- Content from this storage area is cached if a content cache area
is assigned to the same site as the storage area or for content cache
areas that are assigned to different sites than the storage area.
- Cache size
- A cache can automatically purge content that was not accessed
recently.
- Content preloading
- A cache can automatically
load the content of a document when the document is checked in.
Pruning
Pruning is
the activity of deleting content files that were not 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 Maximum Time To Live property)
- Periodic pruning removes content files that were not accessed
for a longer time than the time allowed by the Maximum Time To Live
property. (Document content that is accessed frequently enough can
remain in cache indefinitely.) The pruning occurs automatically halfway
through the period that is specified by the Maximum Time To Live property.
- Mandatory pruning (triggered by the Prune Threshold Size KBytes
property or Prune Threshold Content Elements 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 (Prune
Amount) and the following threshold properties: Prune Threshold Size
KBytes and Prune Threshold Content 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:
- Assign content cache to the same site in which it is created.
Create the content cache area in a site where it can be accessed by the Content Platform Engine servers in that site over a high-speed network, then assign
the content cache area to that same site. Avoid assigning a content cache area from a different
site that is accessed remotely over a slow-speed network.
If you
must administer a remote content cache, the Content Platform Engine
administration console must be able to directly access the content cache, such as through Content Platform Engine to Content Platform Engine
communication. If server communication is not available, use the administration console in the
remote site to manage the content cache.
- Use cache directory for caching.
- Do not store documents in a directory that is designated as a
content cache area. Storing other documents in that directory uses
space that is required for content caching.
- Optimize pruning threshold by using the Prune Threshold Size KBytes
property.
- Set the Prune Threshold Size KBytes 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 by using the Prune Threshold Content
Elements property.
- Determine the number of files that are frequently accessed by
users. Increase that number by 5-10% to determine the maximum number
of files that are 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 used heavily to create documents that are not retrieved later.
- Adjust Maximum Time To Live property.
- Review your system requirements before you set the Maximum Time
To Live 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 content cache area accessible from every Content Platform Engine server in its same
site and to other sites that are assigned to that cache area. It is
not necessary for a cache area's root directory to be accessible from
other sites that contain their own cache area or from the object store
site.
The information that is displayed by the administration
console depends on the server to which the administration console
is connected. No cache area statistics are displayed if the Content Platform Engine server cannot access
the root path of the cache area.
Restriction: Administration of a content cache area requires
access to that area on the file system. You can create a new cache
only through a server that has access to the root path.