user manual

290 BES Developer’s Guide
Connection Management
the ra.xml file. If the configuration property names match, VisiConnect uses
the property-value for the corresponding configuration property name.
Minimizing the Runtime Performance Cost Associated with
Creating Managed Connections
Creating Managed Connections can be expensive depending on the
complexity of the Enterprise Information System (EIS) that the Managed
Connection is representing. As a result, you may decide to populate the
connection pool with an initial number of Managed Connections upon start-up
of Borland Enterprise Server and therefore avoid creating them at run time.
You can configure this setting using the initial-capacity element located in the
ra-borland.xml descriptor file. The default value for this element is 1 Managed
Connection.
As stated in the Connectors 1.0 specification, when an application component
requests a connection to an EIS through the Resource Adapter, VisiConnect
first tries to match the type of connection being requested with any existing
and available Managed Connection in the connection pool. However, if a
match is not found, a new Managed Connection may be created to satisfy the
connection request.
VisiConnect provides a setting to allow a number of additional Managed
Connections to be created automatically when a match is not found. This
feature provides you with the flexibility to control connection pool growth over
time and the performance hit on the server each time this growth occurs. You
can configure this setting using the capacity delta element in the ra-
borland.xml descriptor file. The default value is 1 Managed Connection.
Since no initiating security principal or request context information is known at
VisiConnect start-up, the initial Managed Connections, configured with initial-
capacity, are created with a default security context containing a default
subject and a client request information of null. When additional Managed
Connections configured with capacity-increment are created, the first
Managed Connection is created with the known initiating principal and client
request information of the connection request. The remaining Managed
Connections up to the capacity-delta limit are created using the same default
security context used when creating the initial Managed Connections.
Controlling Connection Pool Growth
As more Managed Connections are created over time, the amount of system
resources such as memory and disk space that each Managed Connection
consumes increases. Depending on the Enterprise Information System (EIS),
this amount may affect the performance of the overall system. To control the
effects of Managed Connections on system resources, Borland Enterprise
Server allows you to configure a setting for the allowed maximum number of
allocated Managed Connections.