IBM Websphere MQ.
IBM MQ is messaging and queuing middleware, with several modes of operation: point-to-point ; publish/subscribe ; file transfer . Applications can publish messages to many subscribers over multicast.
Messaging:
Programs communicate by sending each other data in messages rather than by calling each other directly.
Queuing:
Messages are placed on queues, so that programs can run independently of each other, at different speeds and times, in different locations, and without having a direct connection between them.
The three most important components of the MQ server are:
- The queue manager
- The message queue
- The channel
# QUEUE MANAGER:
A queue manager is a program that provides messaging services to applications. The queue manager ensures that messages are sent to the correct queue or are routed to another queue manager. The queue manager processes both the MQI calls that are issued to it, and the commands that are submitted to it (from whatever source). The queue manager generates the appropriate completion codes for each call or command.
# QUEUE:
A queue is a container for messages. Messages can be retrieved from, or added to, the queue, one at a time, by applications that are connected to the queue manager that owns the queue.
There are four different types of MQ queues and one related object. The four different types of queues are: Local Queue (QL), Remote Queue (QR), Transmission Queue (TQ), and Dead Letter Queue.
When the application App1 wants to send a message to application App2, it opens a queue — the local Queue Manager (QMGR1) determines if it is a Local Queue or a Remote Queue. When App1 issues an MQPUT command to put a message onto the queue, then if the queue is local, the Queue Manager puts the message directly onto that queue. If the queue is a Remote Queue, then the Queue Manager puts the message onto a Transmission Queue.
Message channel definition type
Sender:
A sender channel is a message channel that the queue manager uses to send messages to other queue managers. To send messages using a sender channel, you must also create, on the other queue manager, a receiver channel with the same name as the sender channel. You can also use sender channels with requester channels if you are implementing a “callback” mechanism.
Server:
A server channel is a message channel that the queue manager uses to send messages to other queue managers. To send messages using a server channel, you must also create, on the other queue manager, a receiver channel with the same name as the server channel. You can also use server channels with requester channels. In that case, the requester channel definition at the other end of the channel requests the server channel definition to start. The server sends messages to the requester. The server can also initiate the communication as long as the server knows the connection name of the partner channel.
Receiver:
A receiver channel is a message channel that the queue manager uses to receive messages from other queue managers. To receive messages using a receiver channel, you must also create, on the other queue manager, a sender or a server channel with the same name as this receiver channel.
# CHANNEL:
A channel is a logical communication link, used by distributed queue managers, between two IBM MQ servers.
Message channels
The purpose of a message channel is to transfer messages from one queue manager to another. Message channels are not required by the client server environment.
TYPES OF CHANNEL:
SENDER.
RECEIVER:
SERVER CONNECTION (SVRCONN):
On the server there must be a server connection (SVRCONN) channel available to connect to.
