The system automatically starts a memory dump when certain software or hardware errors occur. You can also request a memory dump, as discussed in the DUMP (Dump Memory), ??MEMDP (Dump Memory), and ??DUMP (Dump Memory) commands. When a memory dump runs, it produces a display that shows the reason for the dump and whether or not the dump is fatal. If a dump is fatal, after the memory dump completes, the system automatically halt/loads. If the memory dump is not fatal, after the memory dump completes, the system starts running again.
| Note: | The system does not perform automatic memory dumps if the OP + NODUMP option is set. For more information about memory dumps, refer to the MDT (Memory Dump Type) command. |
The memory dump procedure can write memory dumps to disk, tape, or CD-R. When a memory dump is to be written to a dump disk file, the memory dump procedure automatically writes the dump to disk. When a memory dump is to be written to tape, the memory dump procedure stops and asks you to specify the tape unit number holding the tape volume on which the memory dump is to be written.
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For a dump to tape, the memory dump procedure automatically selects and uses any write-enabled online scratch tape with the serial number DUMMMP without waiting for you to reply.
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The media used for memory dump to CD-ROM must be scratch: If CD-R media is used it must be new; if CD-RW media is used it must be new or newly erased. Note that no read to verify written data is performed. Do not use media that is known to be unreliable.
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All tape and CD-ROM media are rewound and unloaded when the memory dump process completes or the media is full. These actions are required because the state of the device from an MCP perspective remains as it was preceding the dump. If the dump media is not unloaded, it can be rendered unusable by a user program or MCP process that attempts to use the device when the system resumes following the dump. Ensure that any doors that might inhibit the unloading of the tape or CD-ROM device are open when the dump is directed to such a device.
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When a HLUNIT TAPE <unitnumber> is specified, a Force Dump is able to automatically initiate when a "DUMMMP" scratch tape is mounted on the tape unit. This action enables automatic force dumps to proceed when requested from the MCP on an unattended system.
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If the system attempts to take a memory dump to tape or CD, it waits for an operator to specify a unit number. You must respond to the dump request within 22 hours or the dump may fail to complete normally, in which case, you can halt the partition and force a dump via the console. If the dump process waits longer than 22 hours, system time and date may be incorrect when processing resumes; in this case, please verify the time and date as soon as possible. This situation can be avoided by enabling dump-to-disk or fast dump, as these features do not require operator input during the dump process. Refer to the DN, CM + HLDUMPDISK, or MEMORYCEILING commands to enable these features. Also refer to the OP AUTORUNNING command for managing an unattended system.
Memory Dump to CD-R
Memory dump to CD-ROM is invoked by entering CD <unit number> when prompted SCRATCH TAPE OR CD REQUIRED. If the dump will not fit on a single CD-ROM, you are prompted to provide media for continuation CD-ROMs as needed. The FAMILYNAME of the first CD-ROM containing a memory dump is of the form DP_<date>_<time>. Continuation CDs (if any) are named DP_<date>_<time>_<integer>. Following are examples of names for a three CD dump:
DP_071900_1213 DP_071900_1213_2 DP_071900_1213_3
CD-ROMs containing memory dumps are in a nonstandard format, and will not be able to be read by standard software on other systems such as PCs. The PER CD display distinguishes CD-ROMs that contain memory dumps by appending the phrase, Memory Dump. Certain commands such as FILES and PD do not work on CD-ROMs containing memory dumps.
Memory dump to 650 MB CD-R media, 700 MB CD-R media, DVD-R media, and DVD+R media is supported. MEMDUMP uses the full capacity of whichever media is used. There is no need for the user to specify DENSITY (and no way for the user to specify DENSITY) during MEMDUMP. Continuation media need not be the same capacity as earlier media. SDASUPPORT handles mixed capacity sets while reading MEMDUMPs.
Handling Memory Dumps
The following table describes the system commands that control the way the system handles memory dumps. See Memory Dump Commands for commands that you can use while the memory dump procedure is running.
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Command |
Description |
|---|---|
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CM + HLDUMPDISK |
Directs memory dumps to a dump disk file on the halt/load family. |
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DA |
Starts the DUMPANALYZER system utility. |
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DF |
Empties dump disk files. |
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DL DPFILES |
Directs DUMPDISKMASTER to unload memory dumps from a dump disk file to a disk. |
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DN <file name> |
Directs memory dumps to a dump disk file. |
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DUMP, ??DUMP, and ??MEMDP |
Request that a memory dump be performed. |
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HLUNIT TAPE <unitnumber> |
Enables a Force Dump is able to automatically initiate when a "DUMMMP" scratch tape is mounted on the tape unit. This action enables automatic force dumps to proceed when requested from the MCP on an unattended system. |
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MDT |
Either sets or interrogates the current system-wide memory dump type options. The MDT command enables you to do the following:
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MEMORYCEILING |
Displays the current and maximum memory ceiling values and indicates whether the fast memory dump feature is enabled. |
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OP AUTORUNNING |
The memory dump will be discontinued if it encounters problems such as: the dumpdisk file has insufficient capacity for the dump, or a fatal IO error occurs while writing the dump. For more information, see Handling Dumps to Disk. |
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OP NODUMP |
Determines whether or not memory dumps are to be performed. |
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OP TERMINATE |
Determines whether abnormal terminations, faults, configuration errors, file open failures, and other various error conditions result in a memory dump. |
Memory Dump Performance
The MDT NONCOMPRESSED option was originally implemented to improve performance on systems that could perform the I/O faster than the processor could compress the data. It was not recommended for use on larger systems with faster processors because the option increased the total elapsed time of the dump.
However, in current releases, additional implementation has been added that might provide performance improvements for all systems using the MDT NONCOMPRESSED option. These improvements are based on creating the dump name (DN) file on a multiunit family. When multiple units are utilized for the DN file, simultaneous I/O operations (I/Os) can be performed in parallel, decreasing the elapsed time required to take a complete dump. Because the dump time is not dependent upon the contents of memory, tests can be performed on various configurations to determine the expected time for a given memory dump. In most situations, when the dump is noncompressed, dedicating two units to the DN family results in dumps completing faster. Performance improvements are greatly enhanced by locating the various units on independent paths.
Consider the following when attempting to improve complete memory dump elapsed times by utilizing the MDT NONCOMPRESSED option:
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The memory dump process has a limited number of internal I/O structures for performing parallel I/Os. These internal I/O structures include READ/WRITE operations to active ODT units and to the dump disk file.
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For multiunit families, a minimum of two I/Os and a maximum of 16 I/Os can be performed in parallel. The actual number of parallel I/Os is constrained by the smaller of the number of members in the DN family, a value dependent on the number of ODT units and the maximum value of 16. The second value is calculated by the equation 29(2X), where X is the number of ODT units. The multiple of two derives from the fact that READ and WRITE operations to ODT units need separate I/O structures. For example, if the DN file resides on a four-unit family, a maximum of four I/Os can be performed in parallel. Similarly, if 13 ODT units are in the partition, the equation 29(2*13) limits the maximum to three.
The number of ODT units is based on the current configuration. Therefore, if ODT units are acquired in a partition, but do not really exist, they should be freed from the partition. Refer to the FREE and DOWN commands.
Handling Dumps to Disk
When a memory dump to disk is finished, the system automatically starts a DUMPDISKMASTER job that attempts to unload the dump from the dump disk file. The action that DUMPDISKMASTER takes depends on whether the system option AUTORUNNING (OP 15) is set, or any of the MDT options AUTOSAVE, AUTOUNLOAD, or AUTORUNNING are set, and whether DL DPFILE is specified.
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If MDT AUTOSAVE is set, DUMPDISKMASTER creates a SAVEDUMP file by interfacing with Dumpanalyzer during the unloading of the dump to perform a SAVE command. The file is created on the DL DPFILES disk family if specified, otherwise it is created on the halt load family.
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If MDT AUTOSAVE is reset and OP AUTORUNNING is set, DUMPDISKMASTER creates a raw memory dump image in a DP file. As with the MDT AUTOSAVE command, the file is created on the DL DPFILES disk family if specified, otherwise it is created on the halt load family.
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If both MDT AUTOSAVE and OP AUTORUNNING are reset, DUMPDISKMASTER inspects the MDT AUTOUNLOAD setting. If the option is set, the dump will be unloaded automatically to a DP file on the DL DPFILES family, or as a MEMORY/DUMP tape.
If none of these options are specified, DUMPDISKMASTER prompts the operator for input, by displaying the dump time and reason, with the choices OK, SAVE, PURGE, and SKIP. For an explanation of how to respond to the DUMPDISKMASTER choices, refer to the DF (Empty Dumpdisk File) and DN (Dump Name) commands.
When DUMPDISKMASTER creates a DP or SAVEDUMP disk file, it gives the file a name that includes either the DP or SAVEDUMP prefix and includes the date and time the system performed the dump, as well as the dump reason, in the following format:
DP (or SAVEDUMP)/mmddyy/hhmmss/<reason>
You can check these files with the PD (Print Directory) system command. For example, if DMSIITEST is the name of the DL DPFILES family and the dump was not unloaded with SAVEDUMP action, enter the following syntax to view the dump file:
PD DP/= ON DMSIITEST
The command produces the following response:
DP (DIRECTORY) . 081892 (DIRECTORY) .. 165801(DIRECTORY) ... SC_1 (DATA) . 081992 (DIRECTORY) .. 163532(DIRECTORY) ... SC_1 (DATA)
When DUMPDISKMASTER creates a memory dump tape, it names the tape file MEMORY/DUMP.
Running the DUMPANALYZER System Utility
You can analyze memory dumps by running the SYSTEM/DUMPANALYZER utility program. The DUMPANALYZER utility can analyze dumps stored on MEMORY/DUMP tapes, DP disk files, and saved memory dump disk files created by an earlier DUMPANALYZER run.
To analyze a dump stored on the DL DPFILES family, run DUMPANALYZER and label equate the TAPEIN file to the dump to be analyzed. The following is an example RUN statement:
RUN *SYSTEM/DUMPANALYZER; FILE TAPEIN = DP/mmddyy/hhmmss/<reason> ON <dpfiles family>;
To analyze a memory dump on a MEMORY/DUMP tape, you also run the DUMPANALYZER utility. It expects an input tape file named MEMORY/DUMP by default. To make sure that the program analyzes the correct memory dump, you can label equate the serial number of the tape as follows:
RUN *SYSTEM/DUMPANALYZER; FILE TAPEIN (SERIALNO = <serialno>);
When you run DUMPANALYZER, you can use the DUMPANALYZER SAVE command to produce a disk file that contains the memory dump along with line information and MCP identifier names. This is the form of the memory dump file you can send to your Unisys service representative for evaluation when problems occur. You can copy this saved file to tape with library maintenance. For more information about DUMPANALYZER, refer to the System Software Utilities Operations Reference Manual.
Analyzing Dumps with the EDITOR System Utility
You can analyze memory dumps by loading them into the Editor utility program. You can load any file accepted by DUMPANALYZER, including dumps stored on MEMORY/DUMP tapes, unsaved dumpdisk files, and saved memory dump disk files created by DUMPANALYZER or by the Editor. Use the LOAD DUMP <dump file> syntax to load the dump. For further information, refer to the Editor online help.
