Trap Diagnostic Facility
Today’s Software Diagnostic Tool
with innovative features for the z/OS software developer
Arney Computer Systems
Topics: Dynamic Program Intercepts (DPI)
• Diagnosis with no boundaries
• Intercepting startup
• SVC screening
• PC screening
• Branch Entry Intercept Breakpoints
• Inheritance and pass-through
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Copyright Arney Computer Systems 2012-2014
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Topics: ISPF User Interface
• Menu and panel driven
• Connecting sessions and targeting subtasks
• Symbols
• Single step tracing
• Breakpoints and triggers
• Displaying and zapping storage
• Session recording and scripting
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Copyright Arney Computer Systems 2012-2014
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Topics: Advanced Features
• Program identification
• Dynamic non-interactive tracing
• Grouping tasks into single diagnostic unit
• Remote Debugging Facility
• Amode and Rmode 64-able
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Dynamic Program Intercepts:
Diagnosis with No Boundaries
• Uses z/Architecture Trap Instruction
• Unaffected by applications RTM exits such as
ESTAEX
• Executes in all z/OS environments; task, SRB,
cross memory, locked, and so forth
• Does not require any program modifications
to use any features
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Copyright Arney Computer Systems 2012-2014
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Dynamic Program Intercepts: Startup Intercept
 TDFHOOK startup intercept
• Replace EXEC= for specified system startup
• Specify program as PARM= followed by the
application’s parameters
• Breakpoint is dynamically inserted after
program load and before program is executed
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Copyright Arney Computer Systems 2012-2014
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Dynamic Program Intercepts: SVC Screening
 Allows interception of target programs in
ATTACH,LOAD, LINK and XCTL SVC calls
 Allows interception of RTM exits in SPIE, ESPIE,
STAE, and ESTAE SVC calls
 Inserts automatic system breakpoints in key
points in these calls
 Does not modify any programs
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Copyright Arney Computer Systems 2012-2014
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Dynamic Program Intercepts: PC Screening
 Allows interception of target programs using
ESTAEX
 Allows interception of target programs using
IEAMSCHD to schedule SRBs
 Inserts automatic system breakpoints in key
points in these calls
 Does not modify any programs
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Copyright Arney Computer Systems 2012-2014
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Dynamic Program Intercepts:
Branch Entry Intercept Breakpoints
 Allows interception of branch entry calls such as
SETFRR
 Operates like other dynamic intercepts except it
is specified by a breakpoint
 Set using the BEI command in the User
Interface
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Copyright Arney Computer Systems 2012-2014
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Dynamic Program Intercept:
Inheritance and Pass-Through
 Allows debugging the target program without
hooking any of the programs that attach it
 Target programs that are loaded, linked, or
XCTLed by inherited task are not hooked
 Allows debugging shared code without affecting
non-debugged tasks
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Copyright Arney Computer Systems 2012-2014
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ISPF User Interface: Menu and Panel Driven
 Ease of Use
• Menu items to setup session, gather
diagnostics, and perform utility functions
• Both line mode and panel driven command
entry
• Responses are saved in a memory object
allowing scrolling of prior responses
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Copyright Arney Computer Systems 2012-2014
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ISPF User Interface: Connecting a Session
 Programs in breakpoints are placed in a system
queue
 ISPF list panel shows current list of programs
and their status
 From list, a user can connect, end or release a
dispatchable unit
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Copyright Arney Computer Systems 2012-2014
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ISPF User Interface: Targeting Subtasks and
Shared Code
 Program intercept command allows specifying
target programs for SVC/PC screening
 Program identification command allows
specifying shared code (private and common)
and unidentified code
 Target programs that are loaded, linked, or
xctled by inherited task are not hooked
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Copyright Arney Computer Systems 2012-2014
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ISPF User Interface: Symbols
• Programs are automatically assigned symbols
• Can be user defined
• Can be used in any command instead of an
absolute value
• Can have properties: Name, Value, PC#,
ASN, Length
• Makes a recorded session reusable
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Copyright Arney Computer Systems 2012-2014
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ISPF User Interface: Single Step
• Allows the tracing of a program, instruction by
instruction
• Supports Program Call (PC) and Program
Returns (PR)
• Ranges can be specified to limit the trace to
one or more address ranges
• Automatically skips calls into system code
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Copyright Arney Computer Systems 2012-2014
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ISPF User Interface: Breakpoints
• Setting breakpoints allow stopping a program
at designated points
 Can be set by placing the TDFHOOK
macro in the program source
 Can be set via command
• A command breakpoint is single use and
removed when encountered
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Copyright Arney Computer Systems 2012-2014
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ISPF User Interface: Triggers
• Triggers are breakpoints that trigger setting
another breakpoint
• Used to set a breakpoint in common code
when called from a specific point
• Can only be set by command
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Copyright Arney Computer Systems 2012-2014
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ISPF User Interface: Displaying storage
• Any storage accessible by the debugged task
can be displayed
• Many MVS control blocks can be formatted
using the AS keyword
• Display has commands to display formatted
data such as task structures and PC
structures
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Copyright Arney Computer Systems 2012-2014
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ISPF User Interface: Zapping storage
• Can be entered as a line mode command
• Can be entered in a panel which will retrieve
the verify data allowing confirmation before
the replace
• Can be displayed via a display command and
using the ZAP option overtyped in full screen
mode
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Copyright Arney Computer Systems 2012-2014
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ISPF User Interface: Session Recording
• All commands entered in a session can be
recorded
• Session recording can be edited
• Session recording can be saved and
executed in a later session or at a remote site
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Copyright Arney Computer Systems 2012-2014
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Advanced Features: Program Identification
 Identification of programs reused between
system startups
 Identifying unidentified programs for use in
symbols
 Identifying shared CSA programs for targets in
traps
 Identifying shared code attached multiple times
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Copyright Arney Computer Systems 2012-2014
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Advanced Features: Dynamic Tracing Facility
(Future feature)
 Specifically designed for use in the Remote
Debugging Facility
 Non-interactive collection of specified data
• Specified PSW and state information
• Access, Control and General Purpose
Registers
• Specified data areas up to 2K total size
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Copyright Arney Computer Systems 2012-2014
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Advanced Features: Grouping (Future feature)
• Allows treating any number of tasks across
any number of address spaces as a single
diagnostic unit
• Used in conjunction with dynamic tracing to
resolve complex inter-task issues
• Used in conjunction with symbols and session
recording to create scripts for Remote
Debugging Facility
Click for more information
Copyright Arney Computer Systems 2012-2014
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Advanced Features: Remote Debugging Facility
(Future feature)
 TDF is designed to not only provide the
developer with the ability to debug code but to
also:
• Create scripts that can be executed offsite
with a distributable component
• The offsite user executes job using script
• Data is shipped back and analyzed
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Copyright Arney Computer Systems 2012-2014
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Advanced Features: AMODE and RMODE 64
• Uses server with 64 bit memory object to track
debugging sessions
 Isolates diagnostic storage from application
 Minimizes diagnostic footprint in the
debugged address space
• In, z/OS 1.13 and later, about half of TDF can
execute above the bar
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Copyright Arney Computer Systems 2012-2014
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Trap Diagnostic Facility
Today’s Software Diagnostic Tool
for today’s software developer
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Arney Computer Systems