Operating Systems

Despite IBM’s current policy of support until 2010, several questions concerning the viability of the 3745 (e.g., expertise, spare parts, etc.) will force the issue before then. 

The question for the 3745 user today is, “What’s the best strategy for replacing the 3745 and its functionality?” There are many factors involved in making that decision, such as where the solution should reside and which solution offers the best long-term progression. 

IBM has two offerings for z/OS users and this article compares them: 

  • CCL for Linux
  • Enterprise Extender. 

Neither solution provides total support for all the physical connections and protocols the 3745 supports, but both solutions provide the most-used functions—TN3270 and SNI (System Network Interconnect). 

For users of the old protocols—BSC, S/S, NPSI (except QLLC) XI, etc.— there’s little alternative but to replace the service. The user base is so small there’s no commercial incentive to produce an alternative solution. For some of these services, such as BSC, protocol converters may provide a short-term answer. 

IBM has been coaxing users away from those old protocols for some time. Most have done so or are at least planning to. Certainly, most users of rare protocols (such as airline protocols) have already sought alternatives. 

Even restricting comment to just the supported protocols, several factors could be potentially involved in making a choice, meaning that it’s simply impractical to cover all possible permutations. Instead, we’ll try to look at some of the practical aspects of how each of these solutions can be established and what’s involved in such an implementation. 

Communications Controller for Linux (CCL)  

CCL is what IBM describes as the logical solution. The premise that it’s neither cost-effective nor practical to redevelop the SNA applications is entirely sensible and applicable to any solution. 

CCL involves taking the existing Network Control Program (NCP) and, having removed the Front-End Processor (FEP), running the same code in a Linux Logical Partition (LPAR) or Linux guest under z/VM in a shell (emulator). 

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