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IndexType (MQLONG)

Local Model Alias Remote Cluster
Yes Yes No No No

This specifies the type of index that the queue manager maintains for messages on the queue. The type of index required depends on how the application retrieves messages, and whether the queue is a shared queue or a nonshared queue (see QSGDisp attribute). The following values are possible for IndexType:

MQIT_NONE

No index is maintained by the queue manager for this queue. Use this value for queues that are usually processed sequentially, that is, without using any selection criteria on the MQGET call.

MQIT_MSG_ID

The queue manager maintains an index that uses the message identifiers of the messages on the queue. Use this value queues where the application usually retrieves messages using the message identifier as the selection criterion on the MQGET call.

MQIT_CORREL_ID

The queue manager maintains an index that uses the correlation identifiers of the messages on the queue. Use this value for queues where the application usually retrieves messages using the correlation identifier as the selection criterion on the MQGET call.

MQIT_MSG_TOKEN

The queue manager maintains an index that uses the message tokens of the messages on the queue for use with the workload manager (WLM) functions of z/OS.

You must specify this option for WLM-managed queues; do not specify it for any other type of queue. Also, do not use this value for a queue where an application is not using the z/OS workload manager functions, but is retrieving messages using the message token as a selection criterion on the MQGET call.

MQIT_GROUP_ID

The queue manager maintains an index that uses the group identifiers of the messages on the queue. This value must be used for queues where the application retrieves messages using the MQGMO_LOGICAL_ORDER option on the MQGET call.

A queue with this index type cannot be a transmission queue. A shared queue with this index type must be defined to map to a CFSTRUCT object at CFLEVEL(3) or CFLEVEL(4).

Notes:

  1. The physical order of messages on a queue with index type MQIT_GROUP_ID is not defined, as the queue is optimized for efficient retrieval of messages using the MQGMO_LOGICAL_ORDER option on the MQGET call. This means that the physical order of the messages is not usually the order in which the messages arrived on the queue.

  2. If an MQIT_GROUP_ID queue has a MsgDeliverySequence of MQMDS_PRIORITY, the queue manager uses message priorities zero and one to optimize the retrieval of messages in logical order. As a result, the first message in a group must not have a priority of zero or one; if it does, the message is processed as though it had a priority of two. The Priority field in the MQMD structure is not changed.

For more information about message groups, see the description of the group and segment options in MQGMO - Options field.

The index type that should be used in various cases is shown in Table 83 and Table 84.

Table 83. Recommended or required values of queue index type when MQGMO_LOGICAL_ORDER not specified
Selection criteria on MQGET call Index type for nonshared queue Index type for shared queue
None Any Any
Selection using one identifier:
 
Message identifier MQIT_MSG_ID recommended MQIT_NONE or MQIT_MSG_ID required; MQIT_MSG_ID recommended
Correlation identifier MQIT_CORREL_ID recommended MQIT_CORREL_ID required
Group identifier MQIT_GROUP_ID recommended MQIT_GROUP_ID required
Selection using two identifiers:
 
Message identifier plus correlation identifier MQIT_MSG_ID or MQIT_CORREL_ID recommended MQIT_MSG_ID or MQIT_CORREL_ID required
Message identifier plus group identifier MQIT_MSG_ID or MQIT_GROUP_ID recommended Not supported
Correlation identifier plus group identifier MQIT_CORREL_ID or MQIT_GROUP_ID recommended Not supported
Selection using three identifiers:
 
Message identifier plus correlation identifier plus group identifier MQIT_MSG_ID or MQIT_CORREL_ID or MQIT_GROUP_ID recommended Not supported
Selection using group-related criteria:
 
Group identifier plus message sequence number MQIT_GROUP_ID required MQIT_GROUP_ID required
Message sequence number (must be 1) MQIT_GROUP_ID required MQIT_GROUP_ID required
Selection using message token:
 
Message token for application use Do not use MQIT_MSG_TOKEN
Message token for WLM use MQIT_MSG_TOKEN required Not supported
Table 84. Recommended or required values of queue index type when MQGMO_LOGICAL_ORDER specified
Selection criteria on MQGET call Index type for nonshared queue Index type for shared queue
None MQIT_GROUP_ID required MQIT_GROUP_ID required
Selection using one identifier:
 
Message identifier MQIT_GROUP_ID required Not supported
Correlation identifier MQIT_GROUP_ID required Not supported
Group identifier MQIT_GROUP_ID required MQIT_GROUP_ID required
Selection using two identifiers:
 
Message identifier plus correlation identifier MQIT_GROUP_ID required Not supported
Message identifier plus group identifier MQIT_GROUP_ID required Not supported
Correlation identifier plus group identifier MQIT_GROUP_ID required Not supported
Selection using three identifiers:
 
Message identifier plus correlation identifier plus group identifier MQIT_GROUP_ID required Not supported

To determine the value of this attribute, use the MQIA_INDEX_TYPE selector with the MQINQ call.

This attribute is supported only on z/OS.




 

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