Group message 2 (-GRP2)

Use the Group Message 2 adapter command (-GRP2) for data sources to specify retrieval of message groups and non-group messages from the source queue.


The -GRP2 adapter command enables better control over group messages than the -GRP adapter command. The biggest difference between the -GRP2 and -GRP adapter commands is that -GRP2 can be used to process multiple message groups on the source queue. In addition to this, message groups are processed as a unit with -GRP2 and not as individual messages.

While the -GRP adapter command detects a group on the queue and then starts retrieving messages that belong only to that group, the -GRP2 adapter command detects a group on the queue, retrieves all the messages from that group in a single block of data, and keeps looking for other message groups on the queue and other individual non-group messages.

The following restrictions apply to the -GRP2 adapter command:

  • It has no arguments.
  • It can only be used on input (input cards and GET map function).
  • It cannot be combined with the -GRP adapter command.
  • It assumes usage of the -XGRP, -ALLSEG, and -ALLMSG adapter commands. Whether explicitly specified or not, these three adapter commands will be automatically included by the -GRP2 adapter command.
  • It can be used with the -EQMN and -EQN adapter commands. In case of an error, all messages from the retrieved groups as well as all retrieved non-group messages are moved to the specified error queue.
  • in the Launcher scenario, it can be combined with the -REFRESH adapter command. This is particularly useful when there is a possibility that an incomplete message group gets skipped by the queue cursor in order to obtain another complete message group (or non-group message), and the skipped group later becomes complete.

The following table lists some examples of the -GRP2 adapter command usage.

Presume that the following content of queue QUEUE1 is defined under queue manager QMNAME:

Message ID Message in a group? Group ID Logical Sequence Number Last message in the group? Segmented message? Offset Last Segment? Data
1 NO             PhysMess01
2 YES 1 1 NO NO     PhysMess02
3 YES 1 2 YES NO     PhysMess03
4 NO             PhysMess04
5 YES 1 3 NO NO     PhysMess05
6 YES 2 1 NO NO     PhysMess06
7 NO             PhysMess07
8 NO             PhysMess08
9 YES 2 2 NO YES 0 NO PhysMess09
10 YES 2 2 NO YES 10 NO PhysMess10
11 YES 2 2 NO YES 20 YES PhysMess11
12 YES 2 3 YES NO     PhysMess12
13 YES 3 1 YES NO     PhysMess13
14 NO             PhysMess14

There are few important things to note in this table:

  • Physical messages on positions 1, 4, 7, 8 and 14 are logical messages that do not belong to any group.
  • Physical messages on positions 2, 3 and 5 are logical messages that belong to a group with the group ID equal to "1".
  • Physical messages on positions 6, 9, 10, 11 and 12 belong to a group with the group ID equal to "2". Physical messages on positions 6 and 12 are logical messages, and physical messages on positions 9, 10 and 11 are message segments that together form a single logical message. Physical message on position 11 is the last segment of the logical message. Physical message on position 12 is the last logical message of the group.
  • Physical message on position 13 is a logical message and it belongs to a group with the group ID equal to "3". This message is the only logical message in the group.

Presume that a map has one input card and one output card. The input card is of IBM® MQ type, and the output card is of "File" type. The data content obtained in the input card is stored to a file specified in the output card.