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The user-dened table to use for validation when the validation method is table. Defaults
to test.
If this method is used, the table used should be dedicated only to validation, and the number
of rows in the table should be kept to a minimum.
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Fail All Connections
Indicates whether all connections in the pool are re-created when one is found to be invalid,
or only the invalid one. Only applicable if you have selected a connection validation method.
Disabled by default.
If enabled, all of the re-creation is done in one step, and the thread requesting the
connection is heavily aected. If disabled, the load of re-creating connections is distributed
between the threads requesting each connection.
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Transaction Isolation Level
Species the Transaction Isolation Level on the pooled database connections.
By default, the default isolation level of the connection is left intact. Setting it to any value
does incur the small performance penalty caused by the method call.
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Guarantee Isolation
Only applicable if a transaction isolation level is specied. Defaults to disabled.
Leaving this setting disabled causes the isolation level to be set only when the connection is
created. Enabling sets the level every time the connection is leased to an application. In most
cases, leave this setting disabled.
Tuning the ACL User Cache
The ACL user cache is on by default. Because of the default size of the cache (200 entries), the
ACL user cache can be a bottleneck, or can simply not serve its purpose on a site with heavy
trac. On a busy site, more than 200 users can hit ACL-protected resources in less time than the
lifetime of the cache entries. When this situation occurs, Web Server must query the LDAP
server more often to validate users, which impacts performance.
This bottleneck can be avoided by increasing the maximum users of the ACL cache on the
conguration's Performance tab ⇒ Cache sub tab. You can also set the number of users by
setting the max-users property using the command wadm set-acl-cache-prop. Note that
increasing the cache size uses more resources; the larger you make the cache, the more RAM
you'll need to hold it.
There can also be a potential (but much harder to hit) bottleneck with the number of groups
stored in a cache entry (four by default). If a user belongs to ve groups and hits ve ACLs that
check for these dierent groups within the ACL cache lifetime, an additional cache entry is
created to hold the additional group entry. When there are two cache entries, the entry with the
original group information is ignored.
Tuningthe ACLUserCache
Chapter2 • TuningSunJavaSystemWebServer 77