Browse Prior Art Database

General Trace Facility

IP.com Disclosure Number: IPCOM000078469D
Original Publication Date: 1973-Jan-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 3 page(s) / 47K

Publishing Venue

IBM

Related People

Hunt, TA: AUTHOR

Abstract

Within a complex, multiprogramming Computing System, all hardware/software operations result in the occurrence of definable events, in a specific order. The order of occurrence of these events, at any time, defines the flow of control through the system at that time. To solve problems (both error-type and performance-type) it is often necessary to know both the sequence of the occurrence of these events preceding and during the problem, and to know specific system data related to each event. It is also required that any tool or facility with the capability to provide this information, have no impact on system performance or system resources when not in use.

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General Trace Facility

Within a complex, multiprogramming Computing System, all hardware/software operations result in the occurrence of definable events, in a specific order. The order of occurrence of these events, at any time, defines the flow of control through the system at that time. To solve problems (both error- type and performance-type) it is often necessary to know both the sequence of the occurrence of these events preceding and during the problem, and to know specific system data related to each event. It is also required that any tool or facility with the capability to provide this information, have no impact on system performance or system resources when not in use.

The General Trace Facility (GTF) Subsystem is comprised of two major asynchronous portions: the Disabled Code 1 which gains control when an event occurs, and the GTF Task 2, which is dispatched normally, like other tasks in the system.

The Disabled Code consists of two types, Resident 1a (in the system Nucleus) and Nonresident 1b (dynamically brought into the GTF region when GTF is activated). The Disabled Code gains control when an event occurs, gathers the data for the event and places this data into a buffer 3. When a buffer is full, the GTF Task is signaled. After recording the data, the disabled code returns control to the Event Processor which signaled the event occurrence. The Resident code, which is an extension of the Program First Level Interrupt Handler (PFLIH), executes disabled in Supervisor State, and when GTF is active, branches to the code in the GTF region. This code, too, acts as a logical extension to the Program First Level Interrupt Handler, although it is not resident in the Nucleus. This is the feature of the design that enables GTF to: 1) maximize flexibility, 2) provide information in a greater level of detail and, 3) provide more kinds of data while only requiring minimal code permanently resident in the system. Thus storage is not utilized which could be used by other tasks until the services of GTF are require...