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i kind of don't understand when to use the MQ client connection channel. From my understanding, when client trying to connect MQ server, it can be completed by defining the channel object with server connection channel value directly in application code. Therefore, if so, then why do we need to make use of such client connection channel?

Please help explain to me in detail. Thanks very much

wing2ofsky
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3 Answers3

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A Server Connection Channel is used by clients to connect to a queue manager.

You don't really use a client connection channel to connect to queue manager. A client connection channel defines the connection parameters required to connect to a queue manager for example queue manager name, connection name, SSL etc. These channel definitions are stored in channel definition table (CCDT) files. CCDT files are used by client applications through MQCHLLIB and MQCHLTAB environment variables.

This link and another has little more details.

Shashi
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In older versions of WebSphere MQ, a Client Channel Definition Table was used to specify SSL parameters and for failover so the application could select from several equivalent queue managers at connection time. The CCDT file is a compiled artifact and the DEFINE CHL(channel name) CHLTYPE(CLNTCONN) command is what generates the entries in the CCDT file. So you would only use the CLNTCONN channel type if you wanted to create a CCDT file.

Newer versions of WebSphere MQ expose the CCDT fields in the MQCONNX API and the reconnection parameters are in the CONNAME parameter and the client.ini file. Although these have made the CCDT file obsolete for newer applications, the functionality is still required for commercial and legacy applications. IBM has not announced that CCDT functionality is deprecated and it is in V7.5 which was just released so that functionality will remain for the foreseeable future.

T.Rob
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    Glad to help. Shashi and I are a tag-team. ;-) – T.Rob Jul 04 '12 at 02:10
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    cool!Got it, More and More questions will flood to you guys in future..:-) – wing2ofsky Jul 04 '12 at 02:43
  • Hi Rob, How can i use this in java client? I mean i have client application which try to connect 3 mq managers but I don't know how can i use MQCONNX library in java client? – atul tripathi Nov 08 '17 at 21:50
  • Atul, welcome to Stack Overflow! This site does not work like a forum so there are no threaded discussions here. I see you have asked a couple questions in comments to my answers. Only I am notified for those. Instead, please post these as new questions. Then they will be seen by many people who can answer, and can be found by people who come later looking for the same answer. Be sure to have a look at the [help](https://stackoverflow.com/help) section on what to ask and what not to. – T.Rob Nov 10 '17 at 03:18
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What is a channel?

A channel is a logical communication link between a WebSphere® MQ client and a WebSphere MQ server, or between two WebSphere MQ servers. A channel has two definitions: one at each end of the connection. The same channel name must be used at each end of the connection, and the channel type used must be compatible.

WebSphere® MQ uses two different types of channels:

  1. Message Channel
  2. MQI Channel

A message channel, which is a unidirectional communications link between two queue managers. WebSphere MQ uses message channels to transfer messages between the queue managers. To send messages in both directions, you must define a channel for each direction.

A message channel is a one-way link. It connects two queue managers by using message channel agents (MCAs). Its purpose is to transfer messages from one queue manager to another. Message channels are not required by the client server environment.
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An MQI channel, which is bidirectional and connects an application (MQI client) to a queue manager on a server machine. WebSphere MQ uses MQI channels to transfer MQI calls and responses between MQI clients and queue managers

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Source

Premraj
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    This is all true and is valuable info, but OP was asking about the relationship between SVRCONN and CLNTCONN channels. – T.Rob Nov 10 '17 at 14:59