Attributes of channels stanzas

These attributes determine the configuration of a channel.

This information is not applicable to WebSphere® MQ for the z/OS® platform.

Use the Channels queue manager properties page from the WebSphere MQ Explorer, or the CHANNELS stanza in the qm.ini file, to specify information about channels.

MaxChannels=100 |number
The maximum number of current channels allowed.
The value must be in the range 1 - 65535. The default is 100.
The maximum number of channels allowed to be active at any time. The default is the value specified for the MaxChannels attribute.
MaxInitiators=3 |number
The maximum number of initiators. The default and maximum value is 3.
The binding for applications:
Channels connect using MQCONNX FASTPATH; there is no agent process.
Channels connect using STANDARD.
PipeLineLength=1 |number
The maximum number of concurrent threads a channel will use. The default is 1. Any value greater than 1 is treated as 2.

When you use pipelining, configure the queue managers at both ends of the channel to have a PipeLineLength greater than 1.

Note: Pipelining is only effective for TCP/IP channels.
If WebSphere MQ receives a request to start a channel, but finds that an instance of the channel is already running, in some cases the existing channel instance must be stopped before the new one can start. The AdoptNewMCA attribute allows you to control which types of channels can be ended in this way.
If you specify the AdoptNewMCA attribute for a particular channel type, but the new channel fails to start because a matching channel instance is already running:
  1. The new channel tries to stop the previous one by requesting it to end.
  2. If the previous channel server does not respond to this request by the time the AdoptNewMCATimeout wait interval expires, the thread or process for the previous channel server is ended.
  3. If the previous channel server has not ended after step 2, and after the AdoptNewMCATimeout wait interval expires for a second time, WebSphere MQ ends the channel with a CHANNEL IN USE error.

The AdoptNewMCA functionality applies to server, sender, receiver, and cluster-receiver channels. In the case of a sender or server channel, only one instance of a channel with a particular name can be running in the receiving queue manager. In the case of a receiver or cluster-receiver channel, multiple instances of a channel with a particular name might be running in the receiving queue manager, but only one instance can run at any one time from a particular remote queue manager.

Note: AdoptNewMCA is not supported on requester or server-connection channels.

Specify one or more values, separated by commas or blanks, from the following list:

The AdoptNewMCA feature is not required. This is the default.
Adopt server channels.
Adopt sender channels.
Adopt receiver channels.
Adopt cluster receiver channels.
Adopt all channel types except FASTPATH channels.
Adopt the channel if it is a FASTPATH channel. This happens only if the appropriate channel type is also specified, for example: AdoptNewMCA=RCVR,SVR,FASTPATH.
Attention!: The AdoptNewMCA attribute might behave in an unpredictable fashion with FASTPATH channels. Exercise great caution when enabling the AdoptNewMCA attribute for FASTPATH channels.
AdoptNewMCATimeout=60 |1 - 3600
The amount of time, in seconds, that the new channel instance waits for the old channel instance to end. Specify a value in the range 1 - 3600. The default value is 60.
The type of checking required when enabling the AdoptNewMCA attribute. If possible, perform full checking to protect your channels from being shut down, inadvertently or maliciously. At the very least, check that the channel names match.

Specify one or more of the following values, separated by commas or blanks in the case of QM, NAME, or ALL:

Check that the queue manager names match.

Note that the queue manager name itself is matched, not the QMID.

Check the communications source IP address. For example, the TCP/IP address.
Note: Comma separated CONNAME values apply to target addresses and are, therefore, not relevant to this option.

In the case that a multi-instance queue manager fails over from hosta to hostb, any outbound channels from that queue manager will use the source IP address of hostb. If this is different from hosta, then AdoptNewMCACheck=ADDRESS fails to match.

You can use SSL or TLS with mutual authentication to prevent an attacker from disrupting an existing running channel. Alternatively, use an HACMP type solution with IP-takeover instead of multi-instance queue managers, or use a network load balancer to mask the source IP address.

Check that the channel names match.
Check for matching queue manager names, the communications address, and for matching channel names.

The default is AdoptNewMCACheck=NAME,ADDRESS,QM.