Switching SAG MP option-set COs

An SAG MP option-set CO determines, among other things, which SAG is used, the names of the message partner and SNL endpoint, and which DNs are used to sign and encrypt messages. If a SendMsg or SendFile request that uses real-time mode specifies (either explicitly or by means of an option set) that a particular SAG MP option-set CO is to be used, and if the corresponding scenario encounters one of the following situations, the MSIF transfer service ends the scenario and issues an error event or response message:
  • A real-time SendMsg or SendFile scenario encounters an unrecoverable error related to the SAG configuration (for example, a mandatory option is not specified).
  • A real-time SendMsg or SendFile scenario encounters a recoverable error (these are described in Automatic recovery), but all of its automatic recovery attempts were exhausted.
  • A real-time SendFile scenario encounters an error while attempting to use local file transfer via the MQ Host Adapter as described in File access.
When this happens, the setting of the InErrorAction attribute of the DnfEfaBouParameters CO determines what action the MSIF transfer service is to take:
Event
The MSIF transfer service issues an event and changes the transfer condition of the scenario to inError.
App
If the MSIF transfer service is waiting for an SNL response from the SAG, it generates a response application message and passes it to the application, then changes the transfer state of the scenario to Error_Notif. Otherwise, it issues an event.
Similarly, if an input channel specifies that a particular SAG MP option-set CO is to be used, and if the channel encounters one of the following situations, the MSIF transfer service issues an error event and closes the channel:
  • The input channel encounters an error for which a reopen attempt would normally be made (these are described in Automatic reopen), but it has exhausted all of its automatic reopen attempts.
  • The input channel encounters an error related to the SAG configuration (for example, a mandatory option is not specified).

However, instead of specifying that a particular SAG MP option-set CO is to be used, a scenario or input channel can specify that an SAG MP option-set group is to be used. Then, if one of the situations described previously occurs, the MSIF transfer service does not discontinue the operation but instead switches to the next SAG MP option-set CO in the group and tries again. The MSIF transfer service continues to try different COs until either the operation completes successfully or all of the COs in the group were tried. This mechanism can be used to automatically reroute, to different SAGs, traffic that otherwise would stall.

Notes:
  1. When using SAG MP option-set groups for a SendFile scenario, the file that is to be sent must be shared by all the SAGs in the group. For example, the file must be stored centrally in a shared-file system, and all the SAGs in the group must be configured to have identical SAG directory structures. This assures that the fully qualified name of the file is the same for all of the SAGs in the group.
  2. The SAG MP option-set groups that are used for switching SAG MP option-set COs in SendMsg or SendFile scenarios are the same groups that are used for traffic distribution in MsgReceived, FileReceived, and RespondDownload scenarios, as described in Traffic distribution.
  3. If an MSIF SWIFT operator attempts to open an input channel to an SAG that has an invalid configuration, the MSIF transfer service does not automatically switch the next SAG MP option set CO in the group. In this situation, the operator must either:
    • Correct the SAG configuration and reattempt to open the input channel.
    • Manually switch to another SAG by issuing the set command.
  4. SAG switching can be disabled (see Configuring the SAG switching mode). If disabled, the MSIF transfer service does not automatically switch to the next SAG MP option set CO in the group.

    For example, if you are using the SWIFT feature traffic distribution for inbound transfers, you need to configure SAG MP option-set groups. This automatically activates SAG switching. If you do not want to activate SAG switching for your outbound traffic, but want to use traffic distribution for your inbound traffic, disable SAG switching.

Figure 1 shows an example of a SendFile request that uses an SAG MP option-set group. The transfer option-set CO TOS3 specifies the SAG MP option-set group SMGRP2. The members of SMGRP2 are the SAG MP option set COs SAGMPOS1 and SAGMPOS2. Each of these COs specifies a different SNL ID and, consequently, routes traffic to a different SAG.

Figure 1. Identifying the option-set COs and the SAG MP option-set group to be used in a SendFile scenario
Figure showing how the option-set COs and the SAG MP option-set group to be used in a SendFile scenario are identified
One SAG MP option-set CO in each group is the active CO of that group, that is:
  • The CO that is used first by a new scenario or by an input channel that specifies the group
  • The CO to which a scenario in progress or an input channel that is already open switches, if necessary

When a scenario or input channel switches to a new CO of an SAG MP option-set group, the MSIF transfer service automatically sets that CO to be the new active CO for the group. That is because the old active CO is less likely than the new one to result in a new operation being successful.

The default active CO of a group is the one with the name that is first when sorted alphanumerically. An operator can manually set the active CO for a group by issuing the set command (see set). The administrator who configures an SAG MP option set CO specifies to which group, if any, the CO belongs.

At the beginning of each scenario that uses an SAG MP option-set group, or when an input channel is opened, the MSIF transfer service records the initial option-set CO of that scenario, that is, the CO that the scenario used first. This enables the MSIF transfer service to recognize when all of the COs in a group were tried.

If, while a scenario is in progress or while an input channel is open, an operator manually sets the active CO for its group, and if that scenario or channel needs to switch to another CO, it not only switches to the newly set active CO, but also resets its initial option-set CO to that CO. Consequently, if the scenario or channel needs to switch to another SAG, it will cycle through all of the SAG MP option sets in the group, even ones that it might already have tried. This prevents the manual setting of an active CO from causing a scenario or channel to skip COs that otherwise would have been tried.