Operator/terminal control

Beyond logging or sign-on/sign-out, z/TPF provides facilities for more precise terminal or operator control related to the input/output message stream and application work areas. These facilities are different in the SNA and non-SNA support packages.

Non-SNA support (including ALCI):
  1. For ALCI terminals, an agent assembly area (AAA) (or for 3270 local terminals a routing control block RCB) is permanently assigned (in the fixed file area) to each terminal attached to these lines. No RCBs are assigned to SNA logical units (SDLC terminals). The z/TPF host processor ID renders the RCBs unique in the communications network.
  2. Therefore, each RCB is identified by an address (LNIATA or SLN) and a processor ID. 3270 SNA logical units (SDLC terminals) with pseudo LNIATAs have RCBs assigned in the same manner as real LNIATAs. In order to retrieve a RCB, the communication source program invokes the read AAA/RCB program, which uses the WGTA to retrieve the address of the AAA or RCB.
  3. For MDBF users, each subsystem will have its own unique set of AAA/RCB records. It is probable that each subsystem will also have its own unique set of ordinal numbers for these records. In other words, a terminal that has access to multiple subsystems will most likely have a different record ordinal number in each subsystem. The subsystem ordinal table (SSOR) will be used by WGR to cross-reference a terminal to a subsystem ordinal number.
  4. The RCB contains a system area and an application work area. The system area contains a message assembly area and control fields for proper routing of messages to and from that terminal.
  5. Each RCB is initialized, when its terminal or link becomes active in the system, by the RCB initialization program (RCBI) from information contained in the RCB/AAA initialization table (UAT). You must create the UAT using the system test compiler.
  6. The agent assembly area (AAA) uses the same concept, organization, and accessing method as the RCB. The same UAT and WGTA tables are used for the AAA and for the RCB, simply with a different record type. Non-LNIATA systems do not require AAAs or RCBs.
SNA support:
  1. For messages arriving via SDLC lines, logical unit control, logging information, and message assembly are handled by system records not used by the application; the resource vector table (RVT) and the node control block (NCB). These records must not be used by application programs and are not passed to the application input message editor program when the application is activated.
  2. An application may require a record for work space and for control of message input/output related to the logical unit. When the logical unit consists of multiple work stations, this will usually be essential. The scratch pad area (SPA) is designed for this purpose. There is one for each SNA resource in the network. It may be either a 381-or a 1055-byte record and is undefined except for a standard header and 13 bytes of control data defining the node. All SPAs are initialized via command (ZNSPA) by the SPA initializer program that (1) writes the header (2) copies the 13-byte data item from the resource resolution table (RRT) and (3) zeros the remainder of the block. It is your responsibility to allocate the required space on the fixed file storage for the record size that fits your requirements. The definition of the body of the record and any required initialization is also your responsibility and normally should take place in the application input message editor.
In summary, user requirements for implementing operator or terminal control records are:
  • Allocate the required number of fixed file records via SIP for the chosen configuration, application, and design for the following record types, if used:
    • Routing Control Block
    • Agent Assembly Area
    • AAA Initialization Table (UAT)
    • Scratchpad Area
    • Operator Authorization Table
    • Node Control Block
    • Terminal Application Authorization Table
    • Subsystem Ordinal Record.
  • Create the pilot records, using the system test compiler, for initializing the following records, if used:
    • AAA Initialization Table (UAT)
    • Operator Authorization Table
    • Terminal Application Authorization Table.