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PAGING AND DUMP

Paging space:

To accommodate a large virtual memory space with a limited real memory space, the system uses real memory as a work space and keeps inactive data and programs on disk. The area of the disk that contains this data is called the system paging space.

A page is a unit of virtual memory that holds 4 KB of data and can be transferred between real and auxiliary storage.

A paging space, also called a swap space, is a logical volume with the attribute type equal to paging. This type of logical volume is referred to as a paging space logical volume or simply paging space.

Working of Paging space:

When the amount of free real memory in the system is low, programs or data that have not been used recently are moved from real memory to paging space to release real memory for other activities.

The installation creates a default paging logical volume (hd6) on drive hdisk0, also referred as primary paging space.

The default paging space size is determined during the system customizing phase installation according to the following characteristics:

  1. Paging space can use no less than 64 MB.
  2. If real memory is less than 256 MB, paging space is two times real memory.
  3. If real memory is greater than or equal to 256 MB, paging space is 512 MB.

 Low paging space:

If any of the following messages appear on the console or in response to a command on any terminal, it indicates a low paging space:

“INIT: Paging space is low”

“ksh: cannot fork no swap space”

“Not enough memory”

“Fork function failed”

“fork () system call failed”

“Unable to fork, too many processes”

“Fork failure – not enough memory available”

“Fork function not allowed. Not enough memory available.”

“Cannot fork: Not enough space”

Managing paging space:

The paging logical volume (hd6) is on the first hard disk in rootvg while installation. which contains part or all of the busy / (root) and /usr file systems.

Displaying paging space usage:

class=”fnt”>To display the usage of the paging space, issue the lsps command with the -a parameter.

# lsps -a

Page Space Physical Volume Volume Group Size %Used Active Auto Type

hd6 hdisk0 rootvg 512MB 1 yes yes lv

Increasing paging space:

You can use the chps -s command to dynamically increase the size of a paging space, including hd6.

# chps -s 3 hd6

Reducing paging space:

You can use the chps -d command to dynamically reduce the size of a paging space, including hd6. If you decrease the primary paging space, a temporary boot image and a temporary /sbin/rc.boot pointing to a temporary primary paging space will be created to make sure the system is always in a state where it can be safely rebooted.

# chps -d 1 hd6

O/P

shrinkps: Temporary paging space paging00 created.

shrinkps: Dump device moved to temporary paging space.

shrinkps: Paging space hd6 removed.

shrinkps: Paging space hd6 recreated with new size.

Note:Thechps -dcommand will prevent you from decreasing the size of hd6 below 32 MB or actually deleting it.

Moving the hd6 paging space to another volume group:

Moving a paging space with the name hd6 from rootvg to another volume group is not recommended, because the name is hard-coded in several places.

Moving a paging space within the same VG:

Command used to move the default (hd6) paging space from hdisk0 to hdisk1 within same vg:
# migratepv -l hd6 hdisk0 hdisk1

It take few minutes depending upon the size of memory.

Note: Moving a paging space (including hd6) from the default location to a different disk within the same volume group does not require system reboot.

Removing paging space (not hd6):

To remove a paging space, you have to deactivate the paging space.
You can use the swapoffcommand, which deactivates paging spaces without a reboot.

# swapoff DeviceName { DeviceName … }

Eg: # swapoff /dev/paging03

Important:Paging space need to be similar in size as give in below diagram.

 

Dump:

  • Your system generates a system dump when a severe error occurs.
  • System dumps can also be user-initiated by users with root user authority. A system dump creates a picture of your system’s memory contents.
  • System administrators and programmers can generate a dump and analyze its contents when debugging new applications.

Configure a dump device:

When you install the operating system, the dump device is automatically configured for you. By default, the primary device is /dev/hd6, which is a paging logical volume, and the secondary device is/dev/sysdumpnull.

A primary dump device is a dedicated dump device, while a secondary dump device is shared. The dump device can be configured to either tape or a logical volume on the hard disk to store the system dump.

Note: 1.If you use a paging device for dump devices – only use hd6

If you use a removable device, tape or DVD – be aware that the dump does not span volumes; thus, the dump must fit on a single volume.

3. If your system has 4 GB or more of memory, then the default dump device is /dev/lg_dumplv, and is a dedicated dump device.

Command:

sysdumpdev:-

The sysdumpdev command changes the primary or secondary dump device designation in a system that is running.

To list the current dump destination :

# sysdumpdev -l

Command to change the primary dump device from /dev/hd6 to the logical volume /dev/dumpdev:

# sysdumpdev -P -p /dev/dumpdev

 Determining the size of a dump device :

The size required for a dump is not a constant value, because the system does not dump paging space; only data that resides in real memory can be dumped. Paging space logical volumes will generally hold the system dump.

When a system dump occurs, all of the kernel segment that resides in real memory is dumped (the kernel segment is segment 0). Memory resident user data (such as u-blocks) are also dumped.

The minimum size for the dump space can best be determined using command sysdumpdev -e.

For production systems, it is a good practice to set the size of the dump logical volume to 2GB and above.

Note: If you have confirmed that your dump device type is sysdump, use the extendlv command to increase the space available.

Command:

# sysdumpdev -e

0453-041 Estimated dump size in bytes: 120586240

( The size of the dump device should be at least 120586249 bytes or 115 MB.)

Start a system dump:

The dump can either be system initiated or user initiated.

By pressing Alt+Ctrl+1 or Alt+Ctrl+2 (Key Sequence) or by using SMIT utility dumps can be generated.

System initiated dump:

If your system stops with an 888 number flashing in the operator panel display, the system has generated a dump and saved it to a primary dump device.

Perform the following steps to record the information contained in the 888 sequence message:

  1. Wait until the 888 sequence displays.
  2. Record, in sequence, every code displayed after the 888. On systems with a 3-digit or a 4-digit operator panel, you may need to press the reset button to view the additional digits after the 888. Some systems use an advance button to perform this task, or the increment and decrement buttons.
  3. Stop recording when the 888 reappears.

Likewise: 1. Press reset or increment/decrement buttons

888 (Flashing)
102 ( Ist value)(Indicates an Unexpected System Halt )
Mmm ( 2nd value) ( Indicates the Cause of Halt CRASH CODE)
style=”font-family: ‘Liberation Serif’, serif;”>ddd ( 3rd value)( Indicates the Dump status DUMP CODE)
888 ( 3rd value)

Fig. 1 888 Error Flashing

Crash codes:

The crash codes that follow are part a Type 102 message.they are categorized in three ways:

1) Category1 → Begin the problem determination with software support.

2) Category2 → Begin the problem determination process with hardware support.

3) Category3 → Both software and hardware support may be needed in problem determination.

System Dumps Code:

Code Description
0c0 Dump completed successfully.
0c2 Dump started.
0c3/td>The dump is inhibited.
0c4 Dump completed unsuccessfully. Not enough space available on dump device. Partial dump available.
0c5 Dump failed to start. Unexpected error occurred when attempting to write to dump device.
0c7 Network dump in progress.
0c8 Dump disabled. System configuration does not include a dump device.
0c9 System initiated dump started.

When the system dump completes, the system either halts or reboots, depending upon the setting of the auto restart attribute of sys0.

# lsattr -El sys0 -a autorestart

autorestart true Automatically REBOOT system after a crash True.

You can change this setting by typing the following command.

# chdev -l sys0 -a autorestart=false

sys0 changed

# lsattr -El sys0 -a autorestart

autorestart false Automatically REBOOT system after a crash True.

User initiated dump:

Starting a dump from the command line -

If you initiate the system dump from the command line, use the sysdumpstart command with a -p flag to write to the primary device or a -s flag to write to the secondary device.

# sysdumpstart -p or -s

Starting a dump from the physical control panel -

If an HMC is not connected to your system, you can initiate a system dump by using the physical control panel.

Note : You can use the physical control panel to perform functions such as IPL, power on, and power off.

 

Where,A —–> Power button

B —–> ON/OFF power symbol

C —–> Type and serial number label

D —–> Function/data display

E —–> Serial port 1 connector

F —–> Power on light

A blinking light indicates standby power to the unit.

A constant light indicates full system power to the unit.

G —–> System attention light

H —–> Decrement button

I —–> Enter button

J —–> Increment button

Starting a dump using special key sequences-

You can initiate a dump using the following special key sequences

  • Ctrl-Alt-NumPad1 to write to the primary dump device.
  • Ctrl-Alt-NumPad2 to write to the secondary dump device.

By default, the system will not begin a dump by pressing the special key sequences. To enable dumps via the use of the special key sequences, type

Command:

sysdumpdev -K

Starting a dump from the HMC -

  • On the HMC console, choose the partition you want to dump and press the right mouse button.
  • Select Restart Partition and click the left mouse button; a new screen appears.Screen will appear as given below in fig.3
  • Select Dump and click the OK button to start the dump.

 

Compile and copy System Infomation:

  • The snap command is used to gather configuration information of the system.
  • It provides a convenient method of sending the lslpp and errpt output to your service support center.
  • It gathers the information and compresses the information to a pax file. The file may then be written to a device, such as tape or DVD, or transmitted to a remote system.
  • The information gathered with the snap command might be required to identify and resolve system problems.


Command:

# snap -a -o /dev/rmt0

# /usr/sbin/snap -gfkD -o /dev/rmt0

Options: -c → Compress

-f → File system

-D → Gathers dump and /unix information. The primary dump device is used.

-g → Gathers the output of the lslpp -hac

-k → Gathers kernel information.

-t → Network related issue (TCP/IP)

Before executing the snap -c or snap -o commands, any additional information required by your service support center should be copied to the /tmp/ibmsupt directory.

If you intend to use a tape to send a snap image to IBM for software support, the tape must be one of the following formats:

  • 8 mm, 2.3 GB capacity
  • 8 mm, 5.0 GB capacity
  • 4 mm, 4.0 GB capacity

System Dump Analysis:

The kdb command interprets and formats control structures in the system and provides miscellaneous functions for examining a dump. This command allows you to examine a system dump or a running kernel.

 

Command Syntax :

kdb [flags] [ SystemImageFile [ KernelFile [KernelModule ... ]]]

SystemImageFile  it contains system image

Kernel File  The Kernel file parameter specifies the AIX 5L kernel that kdb will use to resolve kernel symbol definitions. A kernel file must be available. When examining a system dump, it is imperative that the kernel file be the same as the kernel that was used to take the system dump. The default for the Kernel File is /unix.

KernelModule  It contains the file names of any additional kernel that the kdb command uses modules and which are not found in kernel

Eg:-

# kdb /var/adm/ras/vmcore.0 /unix

Note:the kernel file specified on the command line need to be the same kernel file that was running at the time the system dumpwas created.

Paging space:

To accommodate a large virtual memory space with a limited real memory space, the system uses real memory as a work space and keeps inactive data and programs on disk. The area of the disk that contains this data is called the system paging space.

A page is a unit of virtual memory that holds 4 KB of data and can be transferred between real and auxiliary storage.

A paging space, also called a swap space, is a logical volume with the attribute type equal to paging. This type of logical volume is referred to as a paging space logical volume or simply paging space.

Working of Paging space:

When the amount of free real memory in the system is low, programs or data that have not been used recently are moved from real memory to paging space to release real memory for other activities.

The installation creates a default paging logical volume (hd6) on drive hdisk0, also referred as primary paging space.

The default paging space size is determined during the system customizing phase installation according to the following characteristics:

  1. Paging space can use no less than 64 MB.
  2. If real memory is less than 256 MB, paging space is two times real memory.
  3. If real memory is greater than or equal to 256 MB, paging space is 512 MB.

 Low paging space:

If any of the following messages appear on the console or in response to a command on any terminal, it indicates a low paging space:

“INIT: Paging space is low”

“ksh: cannot fork no swap space”

“Not enough memory”

“Fork function failed”

“fork () system call failed”

“Unable to fork, too many processes”

“Fork failure – not enough memory available”

“Fork function not allowed. Not enough memory available.”

“Cannot fork: Not enough space”

Managing paging space:

The paging logical volume (hd6) is on the first hard disk in rootvg while installation. which contains part or all of the busy / (root) and /usr file systems.

Displaying paging space usage:

class=”fnt”>To display the usage of the paging space, issue the lsps command with the -a parameter.

# lsps -a

Page Space Physical Volume Volume Group Size %Used Active Auto Type

hd6 hdisk0 rootvg 512MB 1 yes yes lv

Increasing paging space:

You can use the chps -s command to dynamically increase the size of a paging space, including hd6.

# chps -s 3 hd6

Reducing paging space:

You can use the chps -d command to dynamically reduce the size of a paging space, including hd6. If you decrease the primary paging space, a temporary boot image and a temporary /sbin/rc.boot pointing to a temporary primary paging space will be created to make sure the system is always in a state where it can be safely rebooted.

# chps -d 1 hd6

O/P

shrinkps: Temporary paging space paging00 created.

shrinkps: Dump device moved to temporary paging space.

shrinkps: Paging space hd6 removed.

shrinkps: Paging space hd6 recreated with new size.

Note:Thechps -dcommand will prevent you from decreasing the size of hd6 below 32 MB or actually deleting it.

Moving the hd6 paging space to another volume group:

Moving a paging space with the name hd6 from rootvg to another volume group is not recommended, because the name is hard-coded in several places.

Moving a paging space within the same VG:

Command used to move the default (hd6) paging space from hdisk0 to hdisk1 within same vg:
# migratepv -l hd6 hdisk0 hdisk1

It take few minutes depending upon the size of memory.

Note: Moving a paging space (including hd6) from the default location to a different disk within the same volume group does not require system reboot.

Removing paging space (not hd6):

To remove a paging space, you have to deactivate the paging space.
You can use the swapoffcommand, which deactivates paging spaces without a reboot.

# swapoff DeviceName { DeviceName … }

Eg: # swapoff /dev/paging03

Important:Paging space need to be similar in size as give in below diagram.

 

Dump:

  • Your system generates a system dump when a severe error occurs.
  • System dumps can also be user-initiated by users with root user authority. A system dump creates a picture of your system’s memory contents.
  • System administrators and programmers can generate a dump and analyze its contents when debugging new applications.

Configure a dump device:

When you install the operating system, the dump device is automatically configured for you. By default, the primary device is /dev/hd6, which is a paging logical volume, and the secondary device is/dev/sysdumpnull.

A primary dump device is a dedicated dump device, while a secondary dump device is shared. The dump device can be configured to either tape or a logical volume on the hard disk to store the system dump.

Note: 1.If you use a paging device for dump devices – only use hd6

If you use a removable device, tape or DVD – be aware that the dump does not span volumes; thus, the dump must fit on a single volume.

3. If your system has 4 GB or more of memory, then the default dump device is /dev/lg_dumplv, and is a dedicated dump device.

Command:

sysdumpdev:-

The sysdumpdev command changes the primary or secondary dump device designation in a system that is running.

To list the current dump destination :

# sysdumpdev -l

Command to change the primary dump device from /dev/hd6 to the logical volume /dev/dumpdev:

# sysdumpdev -P -p /dev/dumpdev

 Determining the size of a dump device :

The size required for a dump is not a constant value, because the system does not dump paging space; only data that resides in real memory can be dumped. Paging space logical volumes will generally hold the system dump.

When a system dump occurs, all of the kernel segment that resides in real memory is dumped (the kernel segment is segment 0). Memory resident user data (such as u-blocks) are also dumped.

The minimum size for the dump space can best be determined using command sysdumpdev -e.

For production systems, it is a good practice to set the size of the dump logical volume to 2GB and above.

Note: If you have confirmed that your dump device type is sysdump, use the extendlv command to increase the space available.

Command:

# sysdumpdev -e

0453-041 Estimated dump size in bytes: 120586240

( The size of the dump device should be at least 120586249 bytes or 115 MB.)

Start a system dump:

The dump can either be system initiated or user initiated.

By pressing Alt+Ctrl+1 or Alt+Ctrl+2 (Key Sequence) or by using SMIT utility dumps can be generated.

System initiated dump:

If your system stops with an 888 number flashing in the operator panel display, the system has generated a dump and saved it to a primary dump device.

Perform the following steps to record the information contained in the 888 sequence message:

  1. Wait until the 888 sequence displays.
  2. Record, in sequence, every code displayed after the 888. On systems with a 3-digit or a 4-digit operator panel, you may need to press the reset button to view the additional digits after the 888. Some systems use an advance button to perform this task, or the increment and decrement buttons.
  3. Stop recording when the 888 reappears.

Likewise: 1. Press reset or increment/decrement buttons

888 (Flashing)
102 ( Ist value)(Indicates an Unexpected System Halt )
Mmm ( 2nd value) ( Indicates the Cause of Halt CRASH CODE)
style=”font-family: ‘Liberation Serif’, serif;”>ddd ( 3rd value)( Indicates the Dump status DUMP CODE)
888 ( 3rd value)

Fig. 1 888 Error Flashing

Crash codes:

The crash codes that follow are part a Type 102 message.they are categorized in three ways:

1) Category1 → Begin the problem determination with software support.

2) Category2 → Begin the problem determination process with hardware support.

3) Category3 → Both software and hardware support may be needed in problem determination.

System Dumps Code:

Code Description
0c0 Dump completed successfully.
0c2 Dump started.
0c3/td>The dump is inhibited.
0c4 Dump completed unsuccessfully. Not enough space available on dump device. Partial dump available.
0c5 Dump failed to start. Unexpected error occurred when attempting to write to dump device.
0c7 Network dump in progress.
0c8 Dump disabled. System configuration does not include a dump device.
0c9 System initiated dump started.

When the system dump completes, the system either halts or reboots, depending upon the setting of the auto restart attribute of sys0.

# lsattr -El sys0 -a autorestart

autorestart true Automatically REBOOT system after a crash True.

You can change this setting by typing the following command.

# chdev -l sys0 -a autorestart=false

sys0 changed

# lsattr -El sys0 -a autorestart

autorestart false Automatically REBOOT system after a crash True.

User initiated dump:

Starting a dump from the command line -

If you initiate the system dump from the command line, use the sysdumpstart command with a -p flag to write to the primary device or a -s flag to write to the secondary device.

# sysdumpstart -p or -s

Starting a dump from the physical control panel -

If an HMC is not connected to your system, you can initiate a system dump by using the physical control panel.

Note : You can use the physical control panel to perform functions such as IPL, power on, and power off.

 

Where,A —–> Power button

B —–> ON/OFF power symbol

C —–> Type and serial number label

D —–> Function/data display

E —–> Serial port 1 connector

F —–> Power on light

A blinking light indicates standby power to the unit.

A constant light indicates full system power to the unit.

G —–> System attention light

H —–> Decrement button

I —–> Enter button

J —–> Increment button

Starting a dump using special key sequences-

You can initiate a dump using the following special key sequences

  • Ctrl-Alt-NumPad1 to write to the primary dump device.
  • Ctrl-Alt-NumPad2 to write to the secondary dump device.

By default, the system will not begin a dump by pressing the special key sequences. To enable dumps via the use of the special key sequences, type

Command:

sysdumpdev -K

Starting a dump from the HMC -

  • On the HMC console, choose the partition you want to dump and press the right mouse button.
  • Select Restart Partition and click the left mouse button; a new screen appears.Screen will appear as given below in fig.3
  • Select Dump and click the OK button to start the dump.

 

Compile and copy System Infomation:

  • The snap command is used to gather configuration information of the system.
  • It provides a convenient method of sending the lslpp and errpt output to your service support center.
  • It gathers the information and compresses the information to a pax file. The file may then be written to a device, such as tape or DVD, or transmitted to a remote system.
  • The information gathered with the snap command might be required to identify and resolve system problems.


Command:

# snap -a -o /dev/rmt0

# /usr/sbin/snap -gfkD -o /dev/rmt0

Options: -c → Compress

-f → File system

-D → Gathers dump and /unix information. The primary dump device is used.

-g → Gathers the output of the lslpp -hac

-k → Gathers kernel information.

-t → Network related issue (TCP/IP)

Before executing the snap -c or snap -o commands, any additional information required by your service support center should be copied to the /tmp/ibmsupt directory.

If you intend to use a tape to send a snap image to IBM for software support, the tape must be one of the following formats:

  • 8 mm, 2.3 GB capacity
  • 8 mm, 5.0 GB capacity
  • 4 mm, 4.0 GB capacity

System Dump Analysis:

The kdb command interprets and formats control structures in the system and provides miscellaneous functions for examining a dump. This command allows you to examine a system dump or a running kernel.

 

Command Syntax :

kdb [flags] [ SystemImageFile [ KernelFile [KernelModule ... ]]]

SystemImageFile  it contains system image

Kernel File  The Kernel file parameter specifies the AIX 5L kernel that kdb will use to resolve kernel symbol definitions. A kernel file must be available. When examining a system dump, it is imperative that the kernel file be the same as the kernel that was used to take the system dump. The default for the Kernel File is /unix.

KernelModule  It contains the file names of any additional kernel that the kdb command uses modules and which are not found in kernel

Eg:-

# kdb /var/adm/ras/vmcore.0 /unix

Note:the kernel file specified on the command line need to be the same kernel file that was running at the time the system dumpwas created.

Paging space:

To accommodate a large virtual memory space with a limited real memory space, the system uses real memory as a work space and keeps inactive data and programs on disk. The area of the disk that contains this data is called the system paging space.

A page is a unit of virtual memory that holds 4 KB of data and can be transferred between real and auxiliary storage.

A paging space, also called a swap space, is a logical volume with the attribute type equal to paging. This type of logical volume is referred to as a paging space logical volume or simply paging space.

Working of Paging space:

When the amount of free real memory in the system is low, programs or data that have not been used recently are moved from real memory to paging space to release real memory for other activities.

The installation creates a default paging logical volume (hd6) on drive hdisk0, also referred as primary paging space.

The default paging space size is determined during the system customizing phase installation according to the following characteristics:

  1. Paging space can use no less than 64 MB.
  2. If real memory is less than 256 MB, paging space is two times real memory.
  3. If real memory is greater than or equal to 256 MB, paging space is 512 MB.

 Low paging space:

If any of the following messages appear on the console or in response to a command on any terminal, it indicates a low paging space:

“INIT: Paging space is low”

“ksh: cannot fork no swap space”

“Not enough memory”

“Fork function failed”

“fork () system call failed”

“Unable to fork, too many processes”

“Fork failure – not enough memory available”

“Fork function not allowed. Not enough memory available.”

“Cannot fork: Not enough space”

Managing paging space:

The paging logical volume (hd6) is on the first hard disk in rootvg while installation. which contains part or all of the busy / (root) and /usr file systems.

Displaying paging space usage:

class=”fnt”>To display the usage of the paging space, issue the lsps command with the -a parameter.

# lsps -a

Page Space Physical Volume Volume Group Size %Used Active Auto Type

hd6 hdisk0 rootvg 512MB 1 yes yes lv

Increasing paging space:

You can use the chps -s command to dynamically increase the size of a paging space, including hd6.

# chps -s 3 hd6

Reducing paging space:

You can use the chps -d command to dynamically reduce the size of a paging space, including hd6. If you decrease the primary paging space, a temporary boot image and a temporary /sbin/rc.boot pointing to a temporary primary paging space will be created to make sure the system is always in a state where it can be safely rebooted.

# chps -d 1 hd6

O/P

shrinkps: Temporary paging space paging00 created.

shrinkps: Dump device moved to temporary paging space.

shrinkps: Paging space hd6 removed.

shrinkps: Paging space hd6 recreated with new size.

Note:Thechps -dcommand will prevent you from decreasing the size of hd6 below 32 MB or actually deleting it.

Moving the hd6 paging space to another volume group:

Moving a paging space with the name hd6 from rootvg to another volume group is not recommended, because the name is hard-coded in several places.

Moving a paging space within the same VG:

Command used to move the default (hd6) paging space from hdisk0 to hdisk1 within same vg:
# migratepv -l hd6 hdisk0 hdisk1

It take few minutes depending upon the size of memory.

Note: Moving a paging space (including hd6) from the default location to a different disk within the same volume group does not require system reboot.

Removing paging space (not hd6):

To remove a paging space, you have to deactivate the paging space.
You can use the swapoffcommand, which deactivates paging spaces without a reboot.

# swapoff DeviceName { DeviceName … }

Eg: # swapoff /dev/paging03

Important:Paging space need to be similar in size as give in below diagram.

 

Dump:

  • Your system generates a system dump when a severe error occurs.
  • System dumps can also be user-initiated by users with root user authority. A system dump creates a picture of your system’s memory contents.
  • System administrators and programmers can generate a dump and analyze its contents when debugging new applications.

Configure a dump device:

When you install the operating system, the dump device is automatically configured for you. By default, the primary device is /dev/hd6, which is a paging logical volume, and the secondary device is/dev/sysdumpnull.

A primary dump device is a dedicated dump device, while a secondary dump device is shared. The dump device can be configured to either tape or a logical volume on the hard disk to store the system dump.

Note: 1.If you use a paging device for dump devices – only use hd6

If you use a removable device, tape or DVD – be aware that the dump does not span volumes; thus, the dump must fit on a single volume.

3. If your system has 4 GB or more of memory, then the default dump device is /dev/lg_dumplv, and is a dedicated dump device.

Command:

sysdumpdev:-

The sysdumpdev command changes the primary or secondary dump device designation in a system that is running.

To list the current dump destination :

# sysdumpdev -l

Command to change the primary dump device from /dev/hd6 to the logical volume /dev/dumpdev:

# sysdumpdev -P -p /dev/dumpdev

 Determining the size of a dump device :

The size required for a dump is not a constant value, because the system does not dump paging space; only data that resides in real memory can be dumped. Paging space logical volumes will generally hold the system dump.

When a system dump occurs, all of the kernel segment that resides in real memory is dumped (the kernel segment is segment 0). Memory resident user data (such as u-blocks) are also dumped.

The minimum size for the dump space can best be determined using command sysdumpdev -e.

For production systems, it is a good practice to set the size of the dump logical volume to 2GB and above.

Note: If you have confirmed that your dump device type is sysdump, use the extendlv command to increase the space available.

Command:

# sysdumpdev -e

0453-041 Estimated dump size in bytes: 120586240

( The size of the dump device should be at least 120586249 bytes or 115 MB.)

Start a system dump:

The dump can either be system initiated or user initiated.

By pressing Alt+Ctrl+1 or Alt+Ctrl+2 (Key Sequence) or by using SMIT utility dumps can be generated.

System initiated dump:

If your system stops with an 888 number flashing in the operator panel display, the system has generated a dump and saved it to a primary dump device.

Perform the following steps to record the information contained in the 888 sequence message:

  1. Wait until the 888 sequence displays.
  2. Record, in sequence, every code displayed after the 888. On systems with a 3-digit or a 4-digit operator panel, you may need to press the reset button to view the additional digits after the 888. Some systems use an advance button to perform this task, or the increment and decrement buttons.
  3. Stop recording when the 888 reappears.

Likewise: 1. Press reset or increment/decrement buttons

888 (Flashing)
102 ( Ist value)(Indicates an Unexpected System Halt )
Mmm ( 2nd value) ( Indicates the Cause of Halt CRASH CODE)
style=”font-family: ‘Liberation Serif’, serif;”>ddd ( 3rd value)( Indicates the Dump status DUMP CODE)
888 ( 3rd value)

Fig. 1 888 Error Flashing

Crash codes:

The crash codes that follow are part a Type 102 message.they are categorized in three ways:

1) Category1 → Begin the problem determination with software support.

2) Category2 → Begin the problem determination process with hardware support.

3) Category3 → Both software and hardware support may be needed in problem determination.

System Dumps Code:

Code Description
0c0 Dump completed successfully.
0c2 Dump started.
0c3/td>The dump is inhibited.
0c4 Dump completed unsuccessfully. Not enough space available on dump device. Partial dump available.
0c5 Dump failed to start. Unexpected error occurred when attempting to write to dump device.
0c7 Network dump in progress.
0c8 Dump disabled. System configuration does not include a dump device.
0c9 System initiated dump started.

When the system dump completes, the system either halts or reboots, depending upon the setting of the auto restart attribute of sys0.

# lsattr -El sys0 -a autorestart

autorestart true Automatically REBOOT system after a crash True.

You can change this setting by typing the following command.

# chdev -l sys0 -a autorestart=false

sys0 changed

# lsattr -El sys0 -a autorestart

autorestart false Automatically REBOOT system after a crash True.

User initiated dump:

Starting a dump from the command line -

If you initiate the system dump from the command line, use the sysdumpstart command with a -p flag to write to the primary device or a -s flag to write to the secondary device.

# sysdumpstart -p or -s

Starting a dump from the physical control panel -

If an HMC is not connected to your system, you can initiate a system dump by using the physical control panel.

Note : You can use the physical control panel to perform functions such as IPL, power on, and power off.

 

Where,A —–> Power button

B —–> ON/OFF power symbol

C —–> Type and serial number label

D —–> Function/data display

E —–> Serial port 1 connector

F —–> Power on light

A blinking light indicates standby power to the unit.

A constant light indicates full system power to the unit.

G —–> System attention light

H —–> Decrement button

I —–> Enter button

J —–> Increment button

Starting a dump using special key sequences-

You can initiate a dump using the following special key sequences

  • Ctrl-Alt-NumPad1 to write to the primary dump device.
  • Ctrl-Alt-NumPad2 to write to the secondary dump device.

By default, the system will not begin a dump by pressing the special key sequences. To enable dumps via the use of the special key sequences, type

Command:

sysdumpdev -K

Starting a dump from the HMC -

  • On the HMC console, choose the partition you want to dump and press the right mouse button.
  • Select Restart Partition and click the left mouse button; a new screen appears.Screen will appear as given below in fig.3
  • Select Dump and click the OK button to start the dump.

 

Compile and copy System Infomation:

  • The snap command is used to gather configuration information of the system.
  • It provides a convenient method of sending the lslpp and errpt output to your service support center.
  • It gathers the information and compresses the information to a pax file. The file may then be written to a device, such as tape or DVD, or transmitted to a remote system.
  • The information gathered with the snap command might be required to identify and resolve system problems.


Command:

# snap -a -o /dev/rmt0

# /usr/sbin/snap -gfkD -o /dev/rmt0

Options: -c → Compress

-f → File system

-D → Gathers dump and /unix information. The primary dump device is used.

-g → Gathers the output of the lslpp -hac

-k → Gathers kernel information.

-t → Network related issue (TCP/IP)

Before executing the snap -c or snap -o commands, any additional information required by your service support center should be copied to the /tmp/ibmsupt directory.

If you intend to use a tape to send a snap image to IBM for software support, the tape must be one of the following formats:

  • 8 mm, 2.3 GB capacity
  • 8 mm, 5.0 GB capacity
  • 4 mm, 4.0 GB capacity

System Dump Analysis:

The kdb command interprets and formats control structures in the system and provides miscellaneous functions for examining a dump. This command allows you to examine a system dump or a running kernel.

 

Command Syntax :

kdb [flags] [ SystemImageFile [ KernelFile [KernelModule ... ]]]

SystemImageFile  it contains system image

Kernel File  The Kernel file parameter specifies the AIX 5L kernel that kdb will use to resolve kernel symbol definitions. A kernel file must be available. When examining a system dump, it is imperative that the kernel file be the same as the kernel that was used to take the system dump. The default for the Kernel File is /unix.

KernelModule  It contains the file names of any additional kernel that the kdb command uses modules and which are not found in kernel

Eg:-

# kdb /var/adm/ras/vmcore.0 /unix

Note:the kernel file specified on the command line need to be the same kernel file that was running at the time the system dump was created.