62
WEBSPHERE PORTAL V6.1 TUNING GUIDE
Cache Instances
This section describes the caches in WebSphere Portal V6.1 along with hints to best
configure those caches. As you saw in the modifications we made in our measurement
environments, the size and lifetime properties are the most commonly modified
properties when tuning portal caches. You may wish to increase the size of a cache if many
values are used on a regular basis and there is sufficient space available in the Java heap.
You may wish to increase the lifetime of the entries of a cache if the cached data rarely, if
ever, changes and it is not critical to your business to reflect changes immediately in your
portal.
Each cache description includes the following attributes:
Default size, default lifetime and cache usage pattern
Cache content and scaling factor (i.e. what causes the cache to grow)
Information on the read and write access to the cache
Approximate costs for re-creating cache entries and relative size of cached objects.
Small objects range from 16 to 300 bytes and the largest cache entries are not larger
than a few thousand bytes. One known exception are access control caches in
systems with many resources per user can hold entries that are very large, beyond
50,000 bytes, to reflect all the resources which a user can access.
Some cache descriptions include a sample scenario with suggested property values.
A C C E S S C O N T R O L
1
This section describes each of the access control caches. It is critical for proper operation of
a portal that the access control information be current. Hence it is vital that these caches be
shared within a cluster so that the information is propagated to all members of the cluster.
Different lifetime values should be chosen to avoid concurrent reload of information from
multiple caches. This pattern of rather random lifetime and invalidation intervals could also
be applied to other caches.
The access control caches are divided into two groups: those caches (the first caches in the
list) used during all access control operations in all portal setups and those caches (starting
with the cache com.ibm.wps.ac.ApplicationRoleOIDCache) used for the
WebSphere Portal Composite Application Infrastructure.
1
This section is partially taken from another whitepaper: Portal Access Control Performance Tuning: http://www-
128.ibm.com/developerworks/websphere/library/techarticles/0508_buehler/0508_buehler.html
