Implicit Connection Cache called as ICC in Oracle RAC. ICC
is an advanced JDBC 3.0–compliant connection cache completion for DataSource,
which can position to dissimilar fundamental databases. The cache is facilitated
by invoking setConnectionCacheEnabled(true) on OracleDataSource. Cache is generated
when the first correlation is demanded from the OracleDataSource. ICC produces
and preserves physical connections to the database and enfolds them with
logical connection. One cache is enough to service all connection requests, and
any number of caches can be generated. Preferably, more than one cache is produced
when there is necessitate accessing more than one DataSource. While the ICC
creates and preserves physical connections to the database, the Connection
Cache Manager creates the cache and administers the connection demands to the
cache. ICC provides a number of advantages:
It can be employed with both thin and OCI drivers.
OCI clients can register to accept notifications about RAC
high availability occurrences and respond when events occur.
During DOWN event giving out, OCI ceases affected
connections at the client.
Eliminates connections from the OCI connection pool and the
OCI session pool-the session pool maps each session to a physical connection in
the connection pool, and there can be multiple sessions per connection.
Another feature is Fails over the connection if TAF has been
arranged. If TAF is not configured, then the client only receives an error.
OCI does not currently handle UP events.
There is a one-to-one
mapping between the OracleDataSource instance and the cache. When the
application call ups the close()method to close the connection, all connections
acquired through the datasource are revisited to the cache for reuse. The cache
either returns an existing connection or creates a new connection.
The connection cache holds all properties specified by the
JDBC 3.0 connection pool specification. The support for these properties allows
the application to fine-tune the cache to maximize the performance for each
application.
It also supports a mechanism to recycle and refresh stale
connections. This helps refresh old physical connections.
Only one cache manager is present per virtual machine (VM)
to manage all the caches. The Oracle Connection Cache Manager provides a rich
set of APIs to manage the connection cache.
It provides a connection cache callback mechanism. The
callback feature provides a mechanism for users to define cache actions when a
connection is returned to the cache, when handling abandoned connections, and
when a connection is requested but none is available in the cache.
Public boolean
handleAbandonedConnection(OracleConnection oracleConnection, Object 0): This
function is called when a connection is abandoned.
Public void
releaseConnection(OracleConnection oracleConnection, Object o: This function is
called when releasing a connection.
This mechanism offers the capability for the application to describe
the cache performance when the events occur.
It supports user-defined connection attributes that conclude
which connections are retrieved from the cache. The user characteristics are a
name-value pair and are not validated by the implicit connection cache.
There are two methods can retrieve connections based on
these properties:
getConnection(java.util.Properties
cachedConnectionAttributes)
getConnection(java.lang.String user, java.lang.String
passwd,
java.util.Properties cachedConnectionAttributes)
