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37 DBMS_CONNECTION_POOL

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

See Also:

Oracle Database Concepts for more information on "Database Resident Connection Pooling"

This chapter contains the following topic:


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,
   num_cbrok                IN NUMBER   DEFAULT 1,
   maxconn_cbrok            IN NUMBER   DEFAULT 40000);

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

num_cbrok

Number of brokers to be started at pool start

maxconn_brok

Maximum number of connections for each broker


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.