Linklist is not recommended for Datacom Libraries

Products

• Datacom
• Datacom/DB
• Datacom/AD

Issue/Introduction

As a z/OS Datacom customer, can I place the Datacom loadlibs (CUSLIB and either CAAXLOAD or CABDLOAD) in my Linklist?  

Environment

Datacom/DB

Datacom/AD

Resolution

Datacom libraries are not normally a good choice for placing in your system's Linklist. The Best Practice recommendation is not to use the Linklist library for this product's libraries. 

For this discussion, when we refer to a MUF (Multi-User Facility), we refer to a MUF instance with a unique CXX and MUFname. Data Sharing or MUFPLEX modes A and B are not part of this discussion. Each MUF uses customized load modules which are kept in the CUSLIB allocated to that MUF, and the settings within some of these modules are unique to a specific MUF and cannot be shared.

Many companies have more than one MUF instance running on any given LPAR within one or more SYSPLEX configurations. The reasons for having multiple MUF instances are many; multiple MUFs allow customers to have as much flexibility as needed for Production, Development, and systems environments. There are other conditions in which companies may have different Datacom products that should not be run together within a single MUF.

A production Datacom environment can also have many instances. Broadcom has customers running Datacom with as many as 50 MUFs, and as few as 1 MUF. If a customer has many instances, a common practice is to do what is called "a rolling rollout of maintenance" to a set of MUFs that are in Development and Production. The goal is to certify the maintenance from lesser-used instances to the most-used instances. Eventually, an upgrade to a subsequent release of Datacom will have to be scheduled and performed on each MUF instance. By having private libraries on each MUF instance, you can control when to perform the upgrade process without negatively affecting any of the other MUF instances.

Each upgrade process is unique for a given release of the product. Most of the time spent on an upgrade path has to do with how much work has to run on each Datadictionary (DD), Datadictionary Directory (DDD), and each CXX (Directory). Because each large or small release of the product could have new features or functions which require changes to the DD/DDD, and these have to be cataloged to the CXX, it is important to ensure the definitions are current before beginning the upgrade process. Each unique MUF instance must go through the same process each time the product is upgraded.

Therefore, due to the potential complexity of managing all these different MUF instances, Broadcom recommends that the Datacom loadlibs are not placed in the Linklist and instead, use independent, private libraries within the STEPLIB or JOBLIB JCL. Even with one instance of the MUF running, this is the recommended procedure for running Datacom. It is difficult to predict when your site may require a new MUF instance or when a product may use Datacom/AD in the future. Business requirements lead companies to be dynamic and fluid for any changes and having private libraries gives you the most flexibility to accomplish your business needs.

Additional Information

As always, please contact Broadcom support for Datacom if you have further questions.