DB2 Version 9.7 for Linux, UNIX, and Windows

fcm_num_channels - Number of FCM channels configuration parameter

This parameter specifies the number of FCM channels for each database partition.

Configuration type

Database manager

Applies to

Database server with local and remote clients
Database server with local clients
Partitioned database server with local and remote clients
Satellite database server with local clients

Parameter type

Configurable online

Propagation class

Immediate

Default [range]

UNIX 32-bit platforms: Automatic, with a starting value of 256, 512, or 2048 [128 - 120000 ]
UNIX 64-bit platforms: Automatic, with a starting value of 256, 512, or 2048 [128 - 524288 ]
Windows 32-bit: Automatic, with a starting value of 10000 [128 - 120000 ]
Windows 64-bit: Automatic, with a starting value of 256, 512, or 2048 [128 - 524288 ]

The default starting values for different types of servers are as follows:

Database server with local and remote clients: 512
Database server with local clients: 256
Partitioned database environment server with local and remote clients: 2048

Fast communication manager (FCM) buffers are used for both inter-member and intra-member communications by default. To enable non-clustered database systems to use the FCM subsystem and the fcm_num_channels parameter, you had to set the intra_parallel parameter to YES

An FCM channel represents a logical communication end point between EDUs running in the DB2® engine. Both control flows (request and reply) and data flows (table queue data) rely on channels to transfer data between partitions.

When set to AUTOMATIC, FCM monitors channel usage, incrementally allocating and releasing resources as requirements change.

If you want to set the fcm_num_channels parameter to a specific value with the AUTOMATIC attribute and you do not want the system controller thread to adjust resources lower than the specified value, you need to configure the DB2_FCM_SETTINGS registry variable. To enable this behavior, set the FCM_CFG_BASE_AS_FLOOR option of the DB2_FCM_SETTINGS registry variable to YES (or TRUE). The DB2_FCM_SETTINGS registry variable value is adjusted dynamically.