Analyzing SVC Dumps

This section describes how to analyze SVC dumps using the Diagnostic Summary. Because the summary provides you direct access to much of the information you need for diagnosing the dump, begin your analysis using this screen. Also described are the following screens that you can access from the SVC Diagnostic Summary for additional information about the SVC dump:

• PSW Analysis
• Dump Header Record
• System Diagnostic Work Area
• Task Control Block
• RTM2 Work Area

Online help is available for any Abend-AID Viewer screen, field, system message, or command.

SVC Diagnostic Summary

The SVC Diagnostic Summary screen, shown in the following figures , displays information relating to the abending job. This screen consists of two pages.

SVC Diagnostic Summary 

The following figure shows the second page.

SVC Diagnostic Summary 

To access the diagnostic summary screen, enter S as a line command on the Abend-AID Directory next to the entry for the dump you want to analyze. If you have already selected the dump, do one of the following:

• Directly access the SVC Diagnostic Summary from the Report Menu (Report Menu for SVC Dump Analysis).
• Enter DIAG as a fast-path command on any Abend-AID Viewer screen, and then press Enter.

To analyze the selected SVC dump, do the following:

1. Note information about the dump from the fields displayed on the SVC Diagnostic Summary screen. Information reported for each dump includes the following:First Page

   • Dump Type
   • Completion code
   • Reason code
   • Translation Exception
   • Breaking Event Address Register
   • PSW
   • Active Load Module
   • Entry Point
   • Module Length
   • Address
   • Offset
   • Object Code
   • Mnemonic and Operands

   Second Page

   • Job Name
   • Step Name
   • Procedure Name
   • Date of abend
   • Time of abend
   • Dump Header Record
   • SDWA address
   • TCB requesting dump
   • RTM2 Work Area
   • Storage analysis
   • z/Architecture Extensions
2. Use the cursor point-and-shoot feature to access additional diagnostic information specific to the abend:
   • Press Enter at the Translation Except field to display the Memory Display screen, which is explained in Memory Display.
   • Press Enter at the PSW field to display the PSW Analysis screen. This field contains the Program Status Word at the time of the interrupt. See PSW Analysis Screen.
   • Press Enter at the Entry point field to display the Memory Display screen as described in Memory Display.
   • Press Enter at the Address field to display the Storage Disassembly screen, which is described in Storage Disassembly Screen.
   • Press Enter at the Dump Header Record field to display the Dump Header Record screen, which is described in Dump Header Record Screen.
   • Press Enter at the SDWA address field to display the System Diagnostic Work Area screen, which is described in System Diagnostic Work Area Screen.
   • Press Enter at the TCB requesting dump field to display the Task Control Block screen, which is described in Task Control Block Screen.
   • Press Enter at the RTM2 Work Area field to display the RTM2 Work Area screen, which is described in RTM2 Work Area Screen.
   • Press Enter at the Storage Analysis field to display the MVS Storage Analysis menu, which is described in Analyzing-MVS-Virtual-Storage.
   • Press Enter at the the z/Arch Extensions field to display the Optional z/Achitecture Features screen, which is described in Optional z/Architecture Features Screen.

PSW Analysis Screen

Use the cursor point-and-shoot feauture and press Enter at the PSW field on the SVC Diagnostic Summary Screen to go to the PSW Analysis screen, as shown in PSW Analysis Screen.

The program-status word (PSW) includes the instruction address, condition code, and other information used to control instruction sequencing and to hold and indicate much of the status of the CPU in relation to the program currently being executed.

The Instruction Address is the adjusted next sequential instruction (NSI). If the instruction is a 31-bit address, the high-order bit will be turned off. If the instruction is a 24-bit address, the high-order byte will be set to low values.

Additional control and status information is contained in control registers and permanently assigned storage locations. The active or controlling PSW is called the current PSW. The current PSW in the CPU contains information required for the execution of the currently active program. Bits 0-7 of the PSW are collectively referred to as the system mask.

The full z/Architecture PSW is 128 bits in length. However, in many z/OS control blocks and in the LOAD PSW instruction, the PSW is 64 bits in the format of an ESA/390 PSW except that bit 31 (the z/Architecture extended-addressing-mode bit) may be one. The remainder of this discussion refers to the ESA/390 format of the PSW.

The status of the CPU can be changed by loading a new PSW or part of a PSW. Control is switched during an interruption of the CPU by storing the current PSW, to preserve the status of the CPU, and then loading a new PSW. Execution of LOAD PSW, or the successful conclusion of the initial program-loading sequence, introduces a new PSW. The instruction address is updated by sequential instruction execution and replaced by successful branches. Other instructions are provided which operate on a portion of the PSW. A new or modified PSW becomes active (that is, the information introduced into the current PSW assumes control over the CPU) when the interruption or the execution of an instruction that changes the PSW is completed. The interruption for PER associated with an instruction that changes the PSW occurs under control of the PER mask that is effective at the beginning of the operation.

The CPU has an interruption capability, which permits the CPU to switch rapidly to another program in response to exceptional conditions and external stimuli. When an interruption occurs, the CPU places the current PSW in an assigned location, for the particular class of interruption. The CPU fetches a new PSW from a second assigned storage location. The new PSW determines the next program to be executed. When it has finished processing the interruption, the interrupting program can reload the old PSW, making it again the current PSW, so that the interrupted program can continue.

There are six (6) classes of interruptions: external, I/O, machine check, program, restart, and supervisor call. Each class has a distinct pair of old-PSW, and new-PSW locations permanently assigned in real storage. These storage locations can be found in the Prefixed Save Area (PSA).

PSW Analysis Screen 

Dump Header Record Screen

The Dump Header Record screen, shown in the following figure, displays information from the header record from the currently selected dump.

Dump Header Record Screen 

Use the cursor point-and-shoot feature and press Enter at the 01AC entry in the Offset of SDUMP/SYSMDUMP common field to display the SDUMP/SYSMDUMP Common Section  screen.

SDUMP/SYSMDUMP Common Section Screen

The SDUMP/SYSMDUMP Common Section screen, shown in the following figure, displays information from the SDUMP/SYSMDUMP common section of the header record from the currently selected dump. Access this screen from the Dump Header Record Screen, as described above.

SDUMP/SYSMDUMP Common Section Screen 

Use the cursor point-and-shoot feature and press Enter at REGS field to display the Registers Upon Entry to Dump screen.

Registers Upon Entry to Dump Screen

The Registers Upon Entry to Dump screen, shown in the following figure, displays the contents of the general purpose registers and access registers on entry to the dump.

Registers Upon Entry to Dump Screen 

Use the cursor point-and-shoot feature and press Enter at CR/FPR field to display the Registers Upon Entry to Dump (Control and Floating Point Registers) screen, as shown in the following figure.

Registers Upon Entry to Dump (Control and Floating Point Registers) Screen

The Registers Upon Entry to Dump (Control and Floating Point Registers) screen, as shown in the following figure, displays the contents of the control registers and floating point registers on entry to the dump. Access this screen from the Registers Upon Entry to Dump screen, as described in Registers Upon Entry to Dump Screen above.

Register Upon Entry to Dump (Control and Floating Point Registers) Screen 

Use the cursor point-and-shoot feature and press Enter at the Interpretation field to display the Floating Point Interpretation screen.

Floating Point Interpretation Screen

The Floating Point Interpretation screen, shown in the following figure, displays the content of the 16 floating point registers, along with the value they represent. Access this screen from the Registers Upon Entry to Dump (Control and Floating Point Registers) screen as described above. Alternatively, enter the INTFLOAT fast-path command. This screen shows the interpretation based on one of the following types and formats:

• Decimal Floating Point long format
• Binary Floating Point long format
• Hexadecimal Floating Point long format

Floating Point Interpretation Screen 

In the long format the entire 64 bits of the register represent a floating point number.

Use the cursor point-and-shoot feature and press Enter at the Short, Long, or Extended fields to display the alternate types and formats. An attempt is made to interpret the content of all floating point registers based on the requested combination of type (DFP, BFP, HFP) and format (short, long, extended), but the result is accurate only if the floating point register was being used in that manner. For example, if a floating point register is being used in the extended mode, then the wrong interpretation will be shown if it is displayed in short or long. Similarly, if a floating point register is being used as a decimal FP, then a binary or Hexadecimal interpretation will not yield the correct result.

It is not possible to determine the type or format by examining the content as most content is valid for all combinations but just represents a different value in each combination.

System Diagnostic Work Area Screen

The System Diagnostic Work Area (SDWA) screen, shown in the following figure, displays information from the SDWA. Addresses displayed on this screen are assumed to be from the address space owning SDWA. When displaying areas using the HEXD command, the memory displayed will be from the SDWA owner address space.

System Diagnostic Work Area Screen 

Several of the fields on the SDWA screen show the address for that field and the rest are self-explanatory. Use the cursor point-and-shoot feature to position the cursor on the desired address field and press Enter to access the Memory Display screen, which is described in Memory Display.

Additional text appears at the bottom of the screen that will let you display registers at the time of the error or display the status of the program that established the ESTAE.

Task Control Block Screen

The Task Control Block Screen (TCB), shown in the following figure displays the information from the TCB.

Task Control Block (TCB) Screen 

Many of the fields on the TCB screen show the address for that field and the others are self-explanatory. Use the cursor point-and-shoot feature to position the cursor on the desired address field and press Enter to access the Memory Display screen, which is described in Memory Display.

RTM2 Work Area Screen

The RTM2 Work Area screen, shown in the following figure, describes errors and control flags for sub-functions of task or memory termination within RTM2.

RTM2 Work Area Screen 

Many of the fields on the TCB screen show the address for that field and the others are self-explanatory. Use the cursor point-and-shoot feature to position the cursor on the desired address field and press Enter to access the Memory Display screen, which is described in Memory Display.