Queues

Types of Queues

1. Local Queue

• Messages are stored physically
• All other Queues must be defined to point to a local queue.

Syntax

DEFINE QLOCAL('QUEUE.NAME') DESCR('Description') 

Local Queue can act as below special queues

1. Transmission Queue(XMITQ)

• Local queue with USAGE(XMITQ) attribute
• Directs remote queue messages to other remote Queue Manager.
• If the channel is down/broken, then messages will be present in XMITQ.

Syntax

DEFINE QLOCAL ('XMITQ.NAME')  DESCR('Description') +
TRIGDATA ('CHANNEL.NAME') +
INITQ ('SYSTEM.CHANNEL.INITQ') +
USAGE(XMITQ) +

2. Dead Letter Queue(DEADQ)

• Used for the unpredictable situations when Queue manager is unable to deliver messages to the destination point.

Situations:

• When target queue is unavailable or full
• when target queue doesn't exist
• Authorization issues
• Message is very big

Syntax

DEFINE QLOCAL('DLQ.QUEUE.NAME') DESCR('Description') 

3. Intiation Queue(INITQ)

• Queue manager writes a trigger message using this queue to initiate an action like initiates the channel to start sending messages to another queue manager.

Syntax

DEFINE QLOCAL('INITQ.NAME') DESCR('Description') 

4. Cluster Queue

• Used for advertizing its existence with other queue managers present in the cluster.

Syntax

DEFINE QLOCAL('QUEUE.NAME') DESCR('Description') CLUSTER('CLUSTER.NAME') SHARE 

2. Remote Queue

• Points to a local queue of remote Queue manager.

Syntax

DEFINE QREMOTE ('QREMOTE.NAME') +
       DESCR('Description') +
       PUT(ENABLED) +
       DEFPRTY(0) +
       DEFPSIST(YES) +
       SCOPE(QMGR) +
       RQMNAME(RQMN.NAME) +
       RNAME('RQM.LOCALQ.NAME') +
       XMITQ(XMITQ.NAME) +
       DEFBIND(OPEN) 

3. Model Queue

• It's a template to create a real queue dynamically.

DEFINE QMODEL('MODELQ.NAME') +
DESCR('Description') +
MAXMSGL(4194304) +
MAXDEPTH(500000) +
PROCESS(' ') 

4. Alias Queue

• Pointer to a local queue present in the same Queue manager.
• It can be a pointer to a topic for pub/sub applications.
• Convinient way to hide real queue names from other applications to connect with.

DEFINE QALIAS('ALIASQ.NAME') +
DESCR('Description') +
TARGET('LOCALQ.NAME') 

Note

All the above syntax are for basic understanding only. Attributes for each command can be added based on the requirement.