IBM adds a new layer of communications protocols to SAA for using dispersed databases…
IBM still doesn’t seem to understand that the world has moved on a long way since the 1970s and that its traditional leisurely rate of introduction of new products these days simply means that the number of customers still patiently waiting has dwindled between promise and announcement. As far back as October 1988, IBM promised to make it possible to to access and manage distributed relational data across interconnected Systems Application Architecture systems (SAA itself is of course a concept that needed to have been introduced with the System 34 round about 1977). Two concepts to support access to distributed relational data were introduced with the original SAA announcement: the remote unit of work and distributed unit of work. Last week, a long 21 months later, IBM introduced extensions to the SAA Common Communications Support that provide the architectural basis for remote unit of work access to data distributed across an organisation (CI No 1,455). It also introduced an extension to the Common Programming Interface of SAA to provide a new level of Procedures Language capability remember the three foundation elements of Systems Application Architecture are the Common User Access user interface, Common Communications Support that means compliant applications will talk to each other, and Common Programming Interface that enables the underlying hardware to be changed without disturbing the application.
…explains what it is trying to do…
IBM needs Shirley Temple at her sickliest to do full justice to its acronym crackers and you might have guessed that its latest adventure adds a whole menagerie more: there’s DRDA for Distributed Relational Database Architecture (IBM’s commitment to industry standards is such that it persists in calling the things Data Bases, and its commitment to consistency is such that having called the thing a Data Base, it omits the B from the acronym – how can one hope for data coherence or database consistency from such a company?) And there’s FD:OCA Formatted Data Object Content Architecture; and CDRA for the Character Data Representation Architecture extension to the Common Programming Interface. IBM claims that collectively, the Common Communications Support protocols provide an architected system that provides the customer many benefits – end-users or application programs can easily access information in relational databases from any SAA system or any non-SAA system that implements the Distributed Relational Database Architecture in the enterprise and the customer can access and use data from databases on IBM mainframes, mid-range systems and personal computers geographically dispersed across the organisation. IBM reckons that its enhanced communications support means that data can be transferred between systems interconnected across national language boundaries. The new communications protocols are grouped into six broad categories, IBM suggests. Object Content Architectures enable data objects such as text, graphics and images to be created in a standard format and easily transferred between SAA systems. Data Streams enable programs to generate output destined for a printer, a workstation or another application program elsewhere in the network. Applications Services enhance the activity of the network by providing architectures that enable data distribution, document interchange, and network management. Session Services can be used to enable two applications in the network to establish a dialogue, communicate, and transfer data. Network Services provide assistance in linking across the network. And Data Link Controls are used to establish communications and transmit data across any combination of communications media using local networks, phone links or packet-switched nets. …and describes the protocols in detail
Going into detail on the protocols, DRDA – quick, what does it stand for? – that’s right, Distributed Relational Database Architecture, collectively provides the communications arch
itecture for distributing relational data and extends the power of IBM’s Structured Query Language from one system to a network of connected systems. It prescribes commands, data descriptors, data, objects, communications areas and statements and builds on other Common Communications Support protocols SNA LU 6.2, a new level of Distributed Data Management, the new FD:OCA Formatted Data Object Content Architecture; and CDRA Character Data Representation Architecture. The Logical Unit Type 6.2 Session Service provides communication and transaction processing facilities necessary for distributed relational data, including timely failure notification and propagation of security, authentication, authorisation, and accounting information – well users can attest whether that is true or not because LU 6.2 has been around for a long time. Distributed Data Management is an Applications Service that defines communication facilities interfaces and manages the routing of requests, replies, and data and the new Level 3 architecture for DDM includes a standardised relational database model and an SQL application manager. It packages requests, replies, and formats data into the proper data stream for transmission. FD:OCA no-one’s going to remember that that’s Formatted Data Object Content Architecture, is a new Object Content Architectures protocol designed to provide a consistent way to describe and exchange field-formatted data. Data and its description can be packaged so that it can be understood by the SAA distributed database managers. The description is intended to be attached to the data and transmitted with it, enabling the receiver to interpret the data correctly, without the need for implicit conventions on type, representation, structure or meaning. It defines a broad set of descriptive constructs (or data attributes) used to specify the type, representation and structure of the data, and some additional semantics and is designed to support simple data fields as well as data of high complexity, such as irregular arrays containing elements of different data types. It enables the description of data on an as-is basis, avoiding unnecessary data conversion when data is communicated among like systems. Through its re-use of common data attributes, the FD:OCA data description is concise and efficient – well in IBM terms, anyway. Character Data Representation Architecture, CDRA is a new Data Streams architecture to provide management of graphic character integrity across any pair of SAA database management systems. It defines a consistent method for data identification with unambiguous interpretation of coded graphic characters for data originating in the SAA environments. It defines consistent conversion mappings to help manage the preservation of graphic character integrity as data is interchanged among any pair of databases. It also specifies SAA character sets and code pages. And the SAA Procedures Language has moved up to Level 2. A key extension, IBM says, is native programming language support for stream input and output. Files and a variety of other sources or destinations can be processed as characters or lines of characters. The definition of strings has been extended to include binary notation in addition to the current numeric, character, and hexadecimal notations. A system exits facility has been added to permit applications that use Procedures Language as a macro processor to tailor and control the Procedures Language execution environment. Level 2 is fully implemented in OS/2 Procedures Language 2/REXX, which is available in OS/2 Extended Edition Version 1.2.
