MCA

Message Channel Agent (MCA)

A message channel agent is an IBM MQ program that controls the sending and receiving of messages. Message channel agents move messages from one queue manager to another; there is one message channel agent at each end of a channel.

One MCA takes messages from the transmission queue and puts them on the communication links. The other MCA receives messages and delivers them onto a queue on the remote QMGR.

A message channel agent is called a caller MCA if it initiated the communication, otherwise it is Called a responder MCA.  A caller MCA may be associated with sender, cluster sender, server or requester channel. A responder MCA may be associated with any type of message channel , except a cluster sender.

In MQ Six types of MCA's Available

• Sender MCA (SDR)
• Server MCA (SVR)
• Receiver MCA (RCVR)
• Requester MCA (RQSTR)
• Cluster-sender MCA  (CLUSSDR)
• Cluster-receiver MCA (CLUSRCVR)

Message channel agent type (MCATYPE) : This attribute can specify the message channel agent as a process or a thread.

 Advantages of running as a process include:

• Isolation for each channel providing greater integrity
• Job authority specific for each channel
• Control over job scheduling

Advantages of threads include:

• Much reduced use of storage
• Easier configuration by typing on the command line
• Faster execution - it is quicker to start a thread than to instruct the operating system to start a process

Possible Combinations of message channels

A message channel is a communication link between two queue managers.

A message channel is defined using one of these types defined at one end, and a compatible type at the other end. passable combinations are:

1.SDR-RCVR

2. SDR-RQSTR

3. SVR - RCVR

4. SVR - RQSTR

5. CLUSSDR - CLUSRCVR

Sender -> Initiate connection to receiver

Receiver -> Passive, waits for Initiation sequences from sender

Server-> Initiate connection to receiver, responds for requester

Requester -> Initiate connection then becomes receiver