The resequencer works with two central concepts: groups and sequence IDs. The sequence ID is an identifying part of the message, and messages are rearranged based on this identifier. The messages arriving for resequencing are split into groups and the messages within a group are sequenced according to the sequence ID. Sequencing within a group is independent of the sequencing of messages in any other group. Groups in themselves are not dependent on each other and can be processed independently of each other.

As an example, messages attached to certain groups arrive to a Mediator service component in the following order:

msg9(a), msg8(b), msg7(a), msg6(c), msg5(a), msg4(b), msg3(c), msg2(b), msg1(a)

Table 23-1 shows how the Mediator sorts the messages into groups. The order of the messages in each group depends on the type of resequencer used.

All the groups are processed independently of each other and any error occurring in ones group does not affect the processing of other groups.