IMS Connectivity in an On Demand Environment: A Practical Guide to IMS Connectivity

190 IMS Connectivity in an On Demand Environment: A Practical Guide to IMS Connectivity

The following list describes these options:

 Datastore Groups

A datastore group is a logical collection of datastores. Typically, datastore groups are

constructed to reflect the development life cycle: development, testing, and production.

A datastore can only be a member of one datastore group. Datastore groups are useful

during the construction of transaction routing rules for either transactions or datastores

and for the setting of pacing thresholds.

 Affinity Lists

An affinity list is another logical group of datastores. Typically, affinity lists are constructed

on the basis of workload (transactions). A datastore can be included in more than one

affinity list. It is useful to define affinity lists when constructing transaction routing rules for

either transactions or datastores.

 Applications

An application is a logical collection of transactions. A transaction can only belong to a

single application.

Applications are useful in the construction of transaction routing rules. They simplify the

definition of transaction routing rules by providing default options for all transactions

belonging to the application. If required, transaction routing options can override the

default application routing options.

11.3.1 Transaction routing

Transaction routing allows IMS Connect Extensions to alter the target IMS datastores that

process incoming transaction requests by dynamically changing the target datastore used for

IMS OTMA communication. This improves availability and performance.

An identifier within the incoming transaction request header sent by the client application

normally determines the target IMS datastore for processing. However, IMS Connect

Extensions provides routing by transaction that allows the target IMS datastore to be

substituted with an alternative. IMS Connect Extensions does not route all incoming message

requests. Table 11-1 shows which message types can be routed.

Table 11-1 Routing options for message types

Message type Routing option

Conversational The first message of a conversational transaction can be routed. All

subsequent messages of a conversational transaction will be routed to the

datastore that processed the first message in the conversation.

Non-conversational A non-conversational transaction can be routed.

Send Only A Send Only message can be routed.

Note: If the output from a Send Only is retrieved using RTPIPE then

transaction routing should not be active for these Send Only transactions.

RESUME TPIPE A RTPIPE message

cannot be routed. It will always be directed to the

datastore as defined in the incoming message request.

Ensure transaction routing is inactive for all transactions that create the

asynchronous output or change RTPIPE processing and send RTPIPEs to

all datastores that may have output.

ACK/NAK/DEALLOC All ACKs, NAKs and DEALLOCs will be routed to the datastore that

processed the first message.

Chapter 11. IMS Connect Extensions 191

This dynamic routing is performed using a combination of transaction affinity and datastore

affinity:

 Transaction affinity

Transaction affinity enables you to define on which datastores a transaction can execute.

If the transaction can execute on other datastores, you need to define the transaction and

its affinity processing to IMS Connect Extensions.

Transaction affinity is the list of datastores that are candidates for processing the incoming

transaction. This candidate list can be a single datastore or a list of datastores.

 Datastore affinity

Datastore affinity enables you to create groups of datastores with similar processing

characteristics. For example, datastore affinity can be created for test or production

datastores. By using datastore affinity, a test transaction might benefit from transaction

routing but still be assured it will process only on a test system.

You set these affinities when you define a transaction to IMS Connect Extensions using the

option 7

Transactions in the Definitions menu. Figure 11-18 shows the Transaction panel.

Figure 11-18 Transaction definition panel

This panel enables you to define the datastores where the transaction can be routed using

datastores groups or affinity lists. From this panel, you activate or deactivate the routing

option for a transaction. You also define the response of IMS Connect Extensions when the

transaction routing logic cannot find a datastore to route the message.

You also define affinity when you define a datastore to IMS Connect Extensions using the

option 3

Datastores in the definitions menu. Figure 11-19 on page 192 shows the panel.