Type of index
The queue attribute, IndexType, specifies the type of index that the queue manager maintains to increase the speed of MQGET operations on the queue.
Note: Supported only on IBM MQ for z/OS .We have five options:
| Value | Description |
|---|---|
| NONE | No index is maintained. Use this when retrieving messages sequentially (see Priority ). |
| GROUPID | An index of group identifiers is maintained. We must use this index type if we want logical ordering of message groups (see Logical and physical ordering ). |
| MSGID | An index of message identifiers is maintained. Use this when retrieving messages using the MsgId field as a selection criterion on the MQGET call (see Getting a particular message ). |
| MSGTOKEN | An index of message tokens is maintained. |
| CORRELID | An index of correlation identifiers is maintained. Use this when retrieving messages using the CorrelId field as a selection criterion on the MQGET call (see Getting a particular message ). |
- If we are indexing using the MSGID option or CORRELID option, set the relative MsgId or CorrelId parameters in the MQMD. It is not beneficial to set both.
- Browse uses the index mechanism to find a message if a queue matches all the following conditions:
- It has index type MSGID, CORRELID, or GROUPID
- It is browsed with the same type of id
- It has messages of only one priority
- Avoid queues (indexed by MsgId or CorrelId) containing thousands of messages because this affects restart time. (This does not apply to nonpersistent messages as they are deleted at restart.)
- MSGTOKEN is used to define queues managed by the z/OS workload manager.
For a full description of the IndexType attribute, see IndexType. For further information on the IndexType attribute, see Design and performance considerations for z/OS applications.
Parent topic: Getting messages from a queue