HP OpenVMS Systems Documentation

When an illegal page fault occurs, the stack appears as pictured in Figure 2-5.

Figure 2-5 Stack Following an Illegal Page-Fault Error

The stack contents are as follows:

When you analyze a dump caused by a PGFIPLHI bugcheck, the SHOW STACK command identifies the exception stack frame using the symbols shown in Table 2-8. The SHOW CRASH or CLUE CRASH command displays the instruction that caused the page fault and the instructions around it.

2.8 Inducing a System Failure

If the operating system is not performing well and you want to create a dump you can examine, you must induce a system failure. Occasionally, a device driver or other user-written, kernel-mode code can cause the system to execute a loop of code at a high priority, interfering with normal system operation. This loop can occur even though you have set a breakpoint in the code if the loop is encountered before the breakpoint. To gain control of the system in such circumstances, you must cause the system to fail and then reboot it.

If the system has suspended all noticeable activity and is hung, see the examples of causing system failures in Section 2.8.2.

If you are generating a system failure in response to a system hang, be sure to record the PC and PS as well as the contents of the integer registers at the time of the system halt.

2.8.1 Meeting Crash Dump Requirements

The following requirements must be met before the operating system can write a complete crash dump:

• You must not halt the system until the console dump messages have been printed in their entirety and the memory contents have been written to the crash dump file. Be sure to allow sufficient time for these events to take place or make sure that all disk activity has stopped before using the console to halt the system.
• There must be a crash dump file in SYS$SPECIFIC:[SYSEXE]: named either SYSDUMP.DMP or PAGEFILE.SYS.
  This dump file must be either large enough to hold the entire contents of memory (as discussed in Section 2.2.1.1) or, if the DUMPSTYLE system parameter is set, large enough to accommodate a subset or compressed dump (also discussed in Section 2.2.1.1).
  If SYSDUMP.DMP is not present, the operating system attempts to write crash dumps to PAGEFILE.SYS. In this case, the SAVEDUMP system parameter must be 1 (the default is 0).
• Alternatively, the system must be set up for DOSD. See Section 2.2.1.5, and the OpenVMS System Manager's Manual, Volume 2: Tuning, Monitoring, and Complex Systems for details.
• The DUMPBUG system parameter must be 1 (the default is 1).

This section tells you how to enter the XDelta utility (XDELTA) to force a system failure.

Before you can use XDelta, it must be loaded at system startup. To load XDelta during system bootstrap, you must set bit 1 in the boot flags. See the OpenVMS Alpha Version 7.1 Upgrade and Installation Manual for information about booting with the XDelta utility.

Put the system in console mode by pressing Ctrl/P or the Halt push button. Enter the following commands at the console prompt to enter XDelta:

>>> DEPOSIT SIRR E
>>> CONTINUE

Once you have entered XDelta, use any valid XDelta commands to examine register or memory locations, step through code, or force a system failure (by entering ;C under XDelta). See the OpenVMS Delta/XDelta Debugger Manual for more information about using XDelta.

If you did not load XDelta, you can force a system crash by entering console commands that make the system incur an exception at high IPL. At the console prompt, enter commands to set the program counter (PC) to an invalid address and the PS to kernel mode at IPL 31 before continuing. This results in a forced INVEXCEPTN-type bugcheck. Some Compaq computers employ the console command CRASH (which will force a system failure) while other systems require that you manually enter the commands.

Enter the following commands at the console prompt to force a system failure:

>>> DEPOSIT PC FFFFFFFFFFFFFF00
>>> DEPOSIT PS 1F00
>>> CONTINUE

For more information, refer to the hardware manuals that accompanied your computer.

This chapter describes the format, usage, and qualifiers of the System Dump Analyzer (SDA) utility.

3.1 ANALYZE Usage Summary

The System Dump Analyzer (SDA) utility helps determine the causes of system failures. This utility is also useful for examining the running system.

Format

ANALYZE {/CRASH_DUMP [/RELEASE] [/OVERRIDE] filespec|/SYSTEM} [/SYMBOL = system-symbols-table]

Command Parameter

filespec

Name of the file that contains the dump you want to analyze. At least one field of the filespec is required, and it can be any field. The default filespec is the highest version of SYSDUMP.DMP in your default directory.

Description

By default, the System Dump Analyzer is automatically invoked when you reboot the system after a system failure.

To analyze a system dump interactively, invoke SDA by issuing the following command:

$ ANALYZE/CRASH_DUMP filespec

If you do not specify filespec, SDA prompts you for it.

To analyze a crash dump, your process must have the privileges necessary for reading the dump file. This usually requires system privilege (SYSPRV), but your system manager can, if necessary, allow less privileged processes to read the dump files. Your process needs change-mode-to-kernel (CMKRNL) privilege to release page file dump blocks, whether you use the /RELEASE qualifier or the SDA COPY command.

Invoke SDA to analyze a running system by issuing the following command:

$ANALYZE/SYSTEM

To examine a running system, your process must have change-mode-to-kernel (CMKRNL) privilege. Your process must also have the map-by-PFN privilege (PFNMAP) to access memory by physical address on a running system. You cannot specify filespec when using the /SYSTEM qualifier.

To send all output from SDA to a file, use the SDA command SET OUTPUT, specifying the name of the output file. The file produced is 132 columns wide and is formatted for output to a printer. To later redirect the output to your terminal, use the following command:

SDA> SET OUTPUT SYS$OUTPUT

To send a copy of all the commands you type and a copy of all the output those commands produce to a file, use the SDA command SET LOG, specifying the name of the log file. The file produced is 132 columns wide and is formatted for output to a printer.

To exit from SDA, use the EXIT command. Note that the EXIT command also causes SDA to exit from display mode. Thus, if SDA is in display mode, you must use the EXIT command twice: once to exit from display mode, and a second time to exit from SDA.

The following qualifiers described in this section determine whether the object of an SDA session is a crash dump or a running system. They also help create the environment of an SDA session.

/CRASH_DUMP
/OVERRIDE
/RELEASE
/SYMBOL
/SYSTEM

Invokes SDA to analyze the specified dump file.

Format

/CRASH_DUMP filespec

Parameter

filespec

Name of the crash dump file to be analyzed. The default file specification is:

SYS$DISK:[default-dir]SYSDUMP.DMP

SYS$DISK and [default-dir] represent the disk and directory specified in your last SET DEFAULT command. If you do not specify filespec, SDA prompts you for it.

Description

See Chapter 2, Section 2.3 for additional information on crash dump analysis. You cannot specify the /SYSTEM qualifier when you include the /CRASH_DUMP qualifier in the ANALYZE command.

Examples

$ ANALYZE/CRASH_DUMP SYS$SYSTEM:SYSDUMP.DMP
$ ANALYZE/CRASH SYS$SYSTEM
      

These commands invoke SDA to analyze the crash dump stored in SYS$SYSTEM:SYSDUMP.DMP.

$ ANALYZE/CRASH SYS$SYSTEM:PAGEFILE.SYS
      

This command invokes SDA to analyze a crash dump stored in the system page file.

When used with the /CRASH_DUMP qualifier, invokes SDA to analyze only the structure of the specified dump file when a corruption or other problem prevents normal invocation of SDA with the ANALYZE/CRASH_DUMP command.

Format

/CRASH_DUMP/OVERRIDE filespec

Parameter

filespec

Name of the crash dump file to be analyzed. The default file specification is:

SYS$DISK:[default-dir]SYSDUMP.DMP

SYS$DISK and [default-dir] represent the disk and directory specified in your last SET DEFAULT command. If you do not specify filespec, SDA prompts you for it.

Description

See Chapter 2, Section 2.3 for additional information on crash dump analysis. Note that when SDA is invoked with /OVERRIDE, not all the commands in Chapter 2, Section 2.3 can be used. Commands that can be used are as follows:

• Output control commands such as SET OUTPUT and SET LOG
• Dump file related commands such as SHOW DUMP and CLUE ERRLOG

Commands that cannot be used are as follows:

• Commands that access memory addresses within the dump file such as EXAMINE and SHOW SUMMARY
• The /RELEASE qualifier when you include the /OVERRIDE qualifier in the ANALYZE/CRASH_DUMP command

When /OVERRIDE is used, the SDA command prompt is SDA>>.

Examples

$ ANALYZE/CRASH_DUMP/OVERRIDE SYS$SYSTEM:SYSDUMP.DMP
$ ANALYZE/CRASH/OVERRIDE SYS$SYSTEM
      

These commands invoke SDA to analyze the crash dump stored in SYS$SYSTEM:SYSDUMP.DMP.

Invokes SDA to release those blocks in the specified system page file occupied by a crash dump.

Requires CMKRNL (change-mode-to-kernel) privilege.

Format

/RELEASE filespec

Parameter

filespec

Name of the system page file (SYS$SYSTEM:PAGEFILE.SYS). Because the default file specification is SYS$DISK:[default-dir]SYSDUMP.DMP, you must identify the page file explicitly. SYS$DISK and [default-dir] represent the disk and directory specified in your last DCL command SET DEFAULT. If you do not specify filespec, SDA prompts you for it.

Description

Use the /RELEASE qualifier to release from the system page file those blocks occupied by a crash dump. When invoked with the /RELEASE qualifier, SDA immediately deletes the dump from the page file and allows no opportunity to analyze its contents.

When you specify the /RELEASE qualifier in the ANALYZE command, do the following:

1. Use the /CRASH_DUMP qualifier.
2. Include the name of the system page file (SYS$SYSTEM:PAGEFILE.SYS) as the filespec.

If you do not specify the system page file or the specified page file does not contain a dump, SDA generates the following messages:

%SDA-E-BLKSNRLSD, no dump blocks in page file to release, or not page file %SDA-E-NOTPAGFIL, specified file is not the page file

You cannot specify the /OVERRIDE qualifier when you include the /RELEASE qualifier in the ANALYZE/CRASH_DUMP command.

Example

$ ANALYZE/CRASH_DUMP/RELEASE SYS$SYSTEM:PAGEFILE.SYS
$ ANALYZE/CRASH/RELEASE PAGEFILE.SYS
      

These commands invoke SDA to release to the page file those blocks in SYS$SYSTEM:PAGEFILE.SYS occupied by a crash dump.

Specifies an alternate system symbol table for SDA to use.

Format

/SYMBOL = system-symbol-table

File specification of the OpenVMS Alpha SDA system symbol table required by SDA to analyze a system dump or running system. The specified system-symbol-table must contain those symbols required by SDA to find certain locations in the executive image.

If you do not specify the /SYMBOL qualifier, SDA uses SDA$READ_DIR:SYS$BASE_IMAGE.EXE to load system symbols into the SDA symbol table. When you specify the /SYMBOL qualifier, SDA assumes the default disk and directory to be SYS$DISK:[ ], that is, the disk and directory specified in your last DCL command SET DEFAULT. If you specify a file for this parameter that is not a system symbol table, SDA exits with a fatal error.

Description

The /SYMBOL qualifier allows you to specify a system symbol table to load into the SDA symbol table. You can use the /SYMBOL qualifier whether you are analyzing a system dump or a running system. It is not normally necessary to use the /SYMBOL qualifier when analyzing the running system, since the default SYS$BASE_IMAGE.EXE is the one in use in the system. However if SDA$READ_DIR has been redefined during crash dump analysis, then the /SYMBOL qualifier can be used to ensure that the correct base image is found when analyzing the running system.

The /SYMBOL qualifier can be used with the /CRASH_DUMP and /SYSTEM qualifiers. It is ignored when /OVERRIDE or /RELEASE is specified.

Example

$ ANALYZE/CRASH_DUMP/SYMBOL=SDA$READ_DIR:SYS$BASE_IMAGE.EXE SYS$SYSTEM
      

This command invokes SDA to analyze the crash dump stored in SYS$SYSTEM:SYSDUMP.DMP, using the base image in SDA$READ_DIR.

Invokes SDA to analyze a running system.

Requires CMKRNL (change-mode-to-kernel) privilege. Also requires PFNMAP (map-by-PFN) privilege to access memory by physical address.

Format

/SYSTEM

Parameters

None.

Description

See Chapter 2, Section 2.4 to use SDA to analyze a running system.

You cannot specify the /CRASH_DUMP, /OVERRIDE, or /RELEASE qualifiers when you include the /SYSTEM qualifier in the ANALYZE command.

Example

$  ANALYZE/SYSTEM
      

This command invokes SDA to analyze the running system.

This chapter describes the SDA commands that can be used to analyze a system dump or a running system. SDA CLUE extension commands, which can summarize information provided by certain SDA commands and provide additional detail for some SDA commands, are described in Chapter 5.

The SDA commands are as follows:

@ (Execute Command)
ATTACH
COPY
DEFINE
DEFINE/KEY
DUMP
EVALUATE
EXAMINE
EXIT
FORMAT
HELP
MAP
MODIFY DUMP
READ
REPEAT
SEARCH
SET CPU
SET ERASE_SCREEN
SET FETCH
SET LOG
SET OUTPUT
SET PROCESS
SET RMS
SET SIGN_EXTEND
SET SYMBOLIZE
SHOW ADDRESS
SHOW BUGCHECK
SHOW CALL_FRAME
SHOW CLUSTER
SHOW CONNECTIONS
SHOW CPU
SHOW CRASH
SHOW DEVICE
SHOW DUMP
SHOW EXECUTIVE
SHOW GALAXY
SHOW GCT
SHOW GLOBAL_SECTION_TABLE
SHOW GLOCK
SHOW GMDB
SHOW GSD
SHOW HEADER
SHOW LAN
SHOW LOCKS
SHOW MACHINE_CHECK
SHOW MEMORY
SHOW PAGE_TABLE
SHOW PARAMETER
SHOW PFN_DATA
SHOW POOL
SHOW PORTS
SHOW PROCESS
SHOW RAD
SHOW RESOURCES
SHOW RMD
SHOW RMS
SHOW RSPID
SHOW SHM_CPP
SHOW SHM_REG
SHOW SPINLOCKS
SHOW STACK
SHOW SUMMARY
SHOW SYMBOL
SHOW TQE
SHOW WORKING_SET_LIST
SPAWN
UNDEFINE
VALIDATE PFN_LIST
VALIDATE QUEUE
VALIDATE SHM_CPP

Causes SDA to execute SDA commands contained in a file. Use this command to execute a set of frequently used SDA commands.

Format

@filespec

Parameter

filespec

Name of a file that contains the SDA commands to be executed. The default file type is .COM.

Example

SDA>  @USUAL
      

The Execute command executes the following commands, as contained in a file named USUAL.COM:

SET OUTPUT LASTCRASH.LIS SHOW CRASH SHOW PROCESS SHOW STACK SHOW SUMMARY

This command procedure first makes the file LASTCRASH.LIS the destination for output generated by subsequent SDA commands. Next, the command procedure sends information to the file about the system failure and its context, including a description of the process executing at the time of the failure, the contents of the stack on which the failure occurred, and a list of the processes active on the system.

An EXIT command within a command procedure terminates the procedure at that point, as would an end-of-file.

Command procedures cannot be nested.

Switches control of your terminal from your current process to another process in your job (for example, one created with the SDA SPAWN command).

Format

ATTACH [/PARENT] process-name

Parameter

process-name

Name of the process to which you want to transfer control.

Qualifier

/PARENT

Transfers control of the terminal to the current process parent process. When you specify this qualifier, you cannot specify the process-name parameter.

Examples

SDA>  ATTACH/PARENT
      

This ATTACH command attaches the terminal to the parent process of the current process.

SDA>  ATTACH DUMPER
      

This ATTACH command attaches the terminal to a process named DUMPER in the same job as the current process.

Copies the contents of the dump file to another file.

Format

COPY [/qualifier...] output-filespec

Parameter

output-filespec

Name of the device, directory, and file to which SDA copies the dump file. The default file specification is:

SYS$DISK:[default-dir]filename.DMP

SYS$DISK and [default-dir] represent the disk and directory specified in your last DCL command SET DEFAULT. You must specify a file name.

Qualifiers

/COMPRESS

Causes SDA to compress dump data as it is writing a copy. If the dump being analyzed is already compressed, then SDA does a direct COPY, and issues an informational message indicating that it is ignoring the /COMPRESS qualifier.

/DECOMPRESS

Causes SDA to decompress dump data as it is writing a copy. If the dump being analyzed is already decompressed, then SDA does a direct COPY, and issues an informational message indicating that it is ignoring the /DECOMPRESS qualifier.

Description

Each time the system fails, the contents of memory and the hardware context of the current process (as directed by the DUMPSTYLE parameter) are copied into the file SYS$SYSTEM:SYSDUMP.DMP (or the page file), overwriting its contents. If you do not save this crash dump elsewhere, it will be overwritten the next time that the system fails.

The COPY command allows you to preserve a crash dump by copying its contents to another file. It is generally useful to invoke SDA during system initialization to execute the COPY command. This ensures that a copy of the dump file is made only after the system has failed. The preferred method for doing this, using the logical name CLUE$SITE_PROC, is described in Section 2.2.3.

The COPY command does not affect the contents of the file containing the dump being analyzed.

If you are using the page file (SYS$SYSTEM:PAGEFILE.SYS) as the dump file instead of SYSDUMP.DMP, successful completion of the COPY command will automatically cause the blocks of the page file containing the dump to be released, thus making them available for paging. Even if the copy operation succeeds, the release operation requires that your process have change-mode-to-kernel (CMKRNL) privilege. Once the dump pages have been released from the page file, the dump information in these pages will be lost and SDA will immediately exit. You must perform subsequent analysis upon the copy of the dump created by the COPY command.

If you press Ctrl/T while using the COPY command, the system displays how much of the file has been copied.

Example

SDA>  COPY SYS$CRASH:SAVEDUMP
      

The COPY command copies the dump file into the file SYS$CRASH:SAVEDUMP.DMP.