IBM wants the Internet to talk to mainframes so badly that Big Blue introduced z/OS Connect.
IBM's mainframe strategy for pervasive Internet computing involves discounts on transactions from mobile devices. The company also ensures each major subsystem has a way to communicate with Internet protocols (IP). But Big Blue still wanted more.
Application access points are configured as services identified by URLs. Each service definition points to Extensible Markup Language files that describe the service provider and rules for transforming data between JSON messages and mainframe language structures. The service provider definitions then tell the z/OS Connect servlet how to connect to the back end. For CICS and batch, z/OS Connect uses Websphere Optimized Open Local Adapters. It leverages the IMS-supplied Java Connector Architecture to talk to IMS Connect and then to IMS.
IBM makes z/OS Connect available with WAS, CICS or IMS' Mobile Feature pack. Without CICS or IMS, enterprises need to purchase a WAS or Liberty profile license.
Z/OS Connect also has mainframe-centric features. Among its key abilities is the transformation between JSON and language structures. The process for defining the transformation closely resembles what was developed for CICS: A utility creates a bind file based on the input JSON message or language structure. At run time, z/OS Connect uses the bind file to perform the transformation. Bind files for CICS, IMS and z/OS Connect are interoperable, which implies portability between subsystems. It also provides an option to pass untransformed JSON directly to the back-end system.
IBM z/OS Connect will write type 120.11 records to z/OS System Management Facility (SMF). Installations then track z/OS Connect performance and debug problems. The request ID identifies client messages to the back end. In addition, z/OS Connect interfaces with the System Authorization Facility (SAF), enabling service access control via packages like IBM's RACF or ACF2.
Mainframe shops can also change z/OS Connect's processing through interceptors that are analogous to system exits. Interceptors look at incoming or outgoing request messages and take appropriate action. A systems programmer may define global interceptors for all messages and for a subset. IBM uses interceptors for the SMF and SAF interfaces.
For developers, z/OS Connect supports a discovery service; one call returns all the services defined within z/OS Connect, while a specific service request provides details on how to use it. This lets programmers write mobile applications without knowing all the details about the back end.
Is it worth it?
IBM z/OS Connect is a new and important player in the field of mainframe connectors. IT shops have to weigh the advantages of z/OS Connect against software they already own before purchasing.
CICS recently published a feature pack for Mobile Extensions that seems to functionally overlap with z/OS Connect. And if the past is any indicator, IBM will incorporate the feature pack into a free version of CICS. Integrated JSON support will also allow customers to use their existing infrastructure for exploiting CICS' security, audit and management features. Using CICS as the mobile back end takes advantage of the skillsets of CICS system and application programmers.
IBM's z/OS Connect boasts several advantages; it is a fresh start for providing lightweight services from the mainframe, rather than grafting a solution onto an existing subsystem. It also runs on cost-saving specialty engines; the discovery service makes the mainframe more accessible to non-mainframe programmers and can accelerate development.
About the author:
Robert Crawford spent 29 years as a systems programmer, covering CICS technical support, Virtual Storage Access Method, IBM DB2, IBM IMS and other mainframe products. He programmed in Assembler, Rexx, C, C++, PL/1 and COBOL. Crawford is currently an operations architect based in south Texas, establishing mainframe strategy for a large insurance company.