37 DBMS_CONNECTION_POOL

The DBMS_CONNECTION_POOL package provides an interface to manage Database Resident Connection Pool.

Summary of DBMS_CONNECTION_POOL Subprograms

Table 37-1 DBMS_CONNECTION_POOL Package Subprograms

Subprogram	Description
ALTER_PARAM Procedure	Alters a specific configuration parameter as a standalone unit and does not affect other parameters
CONFIGURE_POOL Procedure	Configures the pool with advanced options
START_POOL Procedure	Starts the pool for operations. It is only after this call that the pool could be used by connection clients for creating sessions
STOP_POOL Procedure	Stops the pool and makes it unavailable for the registered connection clients
RESTORE_DEFAULTS Procedure	Restores the pool to default settings

ALTER_PARAM Procedure

This procedure alters a specific configuration parameter as a standalone unit and does not affect other parameters.

Syntax

DBMS_CONNECTION_POOL.ALTER_PARAM (
   pool_name     IN  VARCHAR2 DEFAULT 'SYS_DEFAULT_CONNECTION_POOL',   param_name    IN  VARCHAR2,   param_value   IN  VARCHAR2);

Parameters

Table 37-2 ALTER_PARAM Procedure Parameters

Parameter	Description
`pool_name`	Pool to be configured. Currently only the default pool name is supported.
`param_name`	Any parameter name from `CONFIGURE_POOL`
`param_value`	Parameter value for `param_name`.

Exceptions

Table 37-3 ALTER_PARAM Procedure Exceptions

Exception	Description
`ORA-56500`	Connection pool not found
`ORA-56504`	Invalid connection pool configuration parameter name
`ORA-56505`	Invalid connection pool configuration parameter value
`ORA-56507`	Connection pool alter configuration failed

Examples

DBMS_CONNECTION_POOL.ALTER_PARAM(
   'SYS_DEFAULT_CONNECTION_POOL', 'MAX_LIFETIME_SESSION', '120');

CONFIGURE_POOL Procedure

This procedure configures the pool with advanced options.

Syntax

DBMS_CONNECTION_POOL.CONFIGURE_POOL (
   pool_name                IN VARCHAR2 DEFAULT 'SYS_DEFAULT_CONNECTION_POOL',
   minsize                  IN NUMBER   DEFAULT 4,
   maxsize                  IN NUMBER   DEFAULT 40,
   incrsize                 IN NUMBER   DEFAULT 2,
   session_cached_cursors   IN NUMBER   DEFAULT 20,
   inactivity_timeout       IN NUMBER   DEFAULT 300,
   max_think_time           IN NUMBER   DEFAULT 120,
   max_use_session          IN NUMBER   DEFAULT 500000,
   max_lifetime_session     IN NUMBER   DEFAULT 86400);

Parameters

Table 37-4 CONFIGURE_POOL Procedure Parameters

Parameter	Description
`pool_name`	Pool to be configured. Currently only the default pool name is supported.
`minsize`	Minimum number of pooled servers in the pool
`maxsize`	Maximum allowed pooled servers in the pool
`incrsize`	Pool would increment by this number of pooled server when pooled server are unavailable at application request time
`session_cached_cursors`	Turn on `SESSION_CACHED_CURSORS` for all connections in the pool. This is an existing `init`.`ora` parameter
`inactivity_timeout`	`TTL` (Time to live) for an idle session in the pool. This parameter helps to shrink the pool when it is not used to its maximum capacity. If a connection remains in the pool idle for this time, it is killed.
`max_think_time`	Maximum time of inactivity by the client after getting a session from the pool. If the client does not issue a database call after grabbing a server from the pool, the client will be forced to relinquish control of the pooled server and will get an `ORA`-`xxxxx` error. The freed up server may or may not be returned to the pool.
`max_use_session`	Maximum number of times a connection can be taken and released to the pool
`max_lifetime_session`	`TTL` (Time to live) for a pooled session

Exceptions

Table 37-5 CONFIGURE_POOL Procedure Exceptions

Exception	Description
`ORA-56500`	Connection pool not found
`ORA-56507`	Connection pool alter configuration failed

Usage Notes

All expressions of time are in seconds
All of the parameters should be set based on statistical request patterns.
minsize should be set keeping in mind that it puts a lower bound on server resource consumption. This is to prevent the timeout from dragging the pool too low, because of a brief period of inactivity.
maxsize should be set keeping in mind that it puts an upper bound on concurrency and response-times and also server resource consumption.
session_cached_cursors is typically set to the number of most frequently used statements. It occupies cursor resource on the server
In doubt, do not set the increment and inactivity_timeout. The pool will have reasonable defaults.
max_use_session and max_lifetime_session allow for software rejuvenation or defensive approaches to potential bugs, leaks, accumulations, and like problems, by getting brand new sessions once in a while.
The connection pool reserves 5% of the pooled servers for authentication, and at least one pooled server is always reserved for authentication. When setting the maxsize parameter, ensure that there are enough pooled servers for both authentication and connections.

START_POOL Procedure

This procedure starts the pool for operations. It is only after this call that the pool could be used by connection classes for creating sessions.

Syntax

DBMS_CONNECTION_POOL.START_POOL (
   pool_name  IN  VARCHAR2 DEFAULT 'SYS_DEFAULT_CONNECTION_POOL');

Parameters

Table 37-6 START_POOL Procedure Parameters

Parameter	Description
`pool_name`	Pool to be started. Currently only the default pool name is supported.

Exceptions

Table 37-7 START_POOL Procedure Exceptions

Exception	Description
`ORA-56500`	Connection pool not found
`ORA-56501`	Connection pool startup failed

Usage Notes

If the instance is restarted (shutdown followed by startup), the pool is automatically started.

STOP_POOL Procedure

This procedure stops the pool and makes it unavailable for the registered connection classes.

Syntax

DBMS_CONNECTION_POOL.STOP_POOL (
   pool_name   IN   VARCHAR2 DEFAULT 'SYS_DEFAULT_CONNECTION_POOL');

Parameters

Table 37-8 STOP_POOL Procedure Parameters

Parameter	Description
`pool_name`	Pool to be stopped. Currently only the default pool name is supported.

Exceptions

Table 37-9 STOP_POOL Procedure Exceptions

Exception	Description
`ORA-56500`	Connection pool not found
`ORA-56506`	Connection pool shutdown failed

Usage Notes

This stops the pool and takes it offline. This does not destroy the persistent data (such as, the pool name and configuration parameters) associated with the pool.

RESTORE_DEFAULTS Procedure

This procedure restores the pool to default settings.

Syntax

DBMS_CONNECTION_POOL.RESTORE_DEFAULTS (
   pool_name   IN  VARCHAR2 DEFAULT 'SYS_DEFAULT_CONNECTION_POOL');

Parameters

Table 37-10 RESTORE_DEFAULTS Procedure Parameters

Parameter	Description
`pool_name`	Pool to be restored. Currently only the default pool name is supported.

Exceptions

Table 37-11 RESTORE_DEFAULTS Procedure Exceptions

Exception	Description
`ORA-56500`	Connection pool not found
`ORA-56507`	Connection pool alter configuration failed

Usage Notes

If the instance is restarted (shutdown followed by startup), the pool is automatically started.