You can use the JES-defined attachment providing there is not an adverse impact on JES performance. JES requires high-speed delivery of any messages that it sends. If you use the attachment to send large volumes of data (messages) from one member to another, you can expect an impact on JES performance.

Consider the following analogy: Years back, you decided to operate your small, single-agent real estate business from your home. Your spouse was away during the day at work. On a lean budget, you couldn't justify a second phone line although telephone calls were crucial to your business. Rarely did personal phone calls interrupt your use of the phone, in any case. As business increased, your spouse began working only part time, and the children grew. Inevitably, your family's increased use and your decreased access to the telephone began impacting your business; a second phone line became necessary. The second line, of course, accessed the same company you were using and provided all the same services. Two connections to the same set of services allowed all the required communication your household needed, without disrupting your business or the family's social environment.

Your need for a second attachment to JES XCF is very similar. The best way to start is to use the JES attachment. That is, you need not code exit IXZXIT03 to attach to the existing JES group to use the attachment. The JES XCF group is created automatically by JES in JES Version 5 and is available for your use. Once you are using the attachment, monitor JES performance. If JES performance is adversely impacted, code exit IXZXIT03 to create your own attachment to the JES common coupling service. To use the JES-defined attachment, you need to retrieve the JES XCF group token that identifies the JES XCF group and member name.