Channel control function

Channel control function

The channel control function provides facilities for you to define, monitor, and control channels.

Commands are issued through panels, programs, or from a command line to the channel control function. The panel interface also displays channel status and channel definition data. We can use Programmable Command Formats or those IBM MQ commands (MQSC) and control commands that are detailed in Monitor and controlling channels on UNIX, Linux, and Windows.
The commands fall into the following groups:

Channel administration
Channel control
Channel status monitoring
Channel administration commands deal with the definitions of the channels. They enable you to:

Create a channel definition
Copy a channel definition
Alter a channel definition
Delete a channel definition
Channel control commands manage the operation of the channels. They enable you to:

Start a channel
Stop a channel
Re-synchronize with partner (in some implementations)
Reset message sequence numbers
Resolve an in-doubt batch of messages
Ping; send a test communication across the channel
Channel monitoring displays the state of channels, for example:

Current channel settings
Whether the channel is active or inactive
Whether the channel terminated in a synchronized state

For more information about defining, controlling and monitoring channels, see the following subtopics:

Preparing channels
Before trying to start a message channel or MQI channel, you must prepare the channel. You must make sure that all the attributes of the local and remote channel definitions are correct and compatible.
Channel states
A channel can be in one of many states at any time. Some states also have substates. From a given state a channel can move into other states.
Server-connection channel limits
We can set server-connection channel limits to prevent client applications from exhausting queue manager channel resources, MAXINST, and to prevent a single client application from exhausting server-connection channel capacity, MAXINSTC.
Checking that the other end of the channel is still available
We can use the heartbeat interval, the keep alive interval, and the receive timeout, to check that the other end of the channel is available.
Adopting an MCA
The Adopt MCA function enables IBM MQ to cancel a receiver channel and start a new one in its place.
Stop and quiescing channels
We can stop and quiesce a channel before the disconnect time interval expires.
Restarting stopped channels
When a channel goes into STOPPED state, we have to restart the channel manually.
In-doubt channels
An in-doubt channel is a channel that is in doubt with a remote channel about which messages have been sent and received.
Problem determination
There are two distinct aspects to problem determination - problems discovered when a command is being submitted, and problems discovered during operation of the channels.
Parent topic: Introduction to distributed queue management