aix paging and dump

7/23/2019 AIX Paging and Dump

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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 eual to

paging. This type of logical volume is referred to as a paging space logical volume or simply

paging space.

Working of Paging space:

!hen 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 "hd#$ on drive hdisk%, also referred

as primary paging space.

The default paging space si&e is determined during the system customi&ing 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 t!o times realmemory.

". If real memory is #reater than or e$ual to 256 MB paging space is 512MB.

Low paging space:

(f any of the following messages appear on the console or in response to a command on any

terminal, it indicates a low paging space'

)(*(T' Paging space is low+

)ksh' cannot fork no swap space+

)*ot enough memory+



)ork function failed+

)fork "$ system call failed+

)-nable to fork, too many processes+

)ork failure not enough memory available+

)ork function not allowed. *ot enough memory available.+

)/annot fork' *ot enough space+

Managing paging space:

The paging logical volume "hd#$ is on the first hard disk in rootvg while installation. which

contains part or all of the busy 0 "root$ and 0usr file systems.

Displaying paging space usage:

class1+fnt+2To display the usage of the paging space, issue the lsps command with the 3a

parameter.

# lsps -a

Page pace 5hysical 6olume 6olume 7roup i&e 8-sed Active Auto Type

hd# hdisk% rootvg 9:;<B : yes yes lv

Increasing paging space:

=ou can use the chps -s command to dynamically increase the si&e of a paging space,

including hd#.

> chps 3s ? hd#

Reducing paging space:

=ou can use the chps -d command to dynamically reduce the si&e of a paging space,

including hd#. (f you decrease the primary paging space, a temporary boot image and a

temporary /sbin/rcboo! 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 3d : hd#

"/P

shrinkps: Temporary paging space paging%% created.



shrinkps: Dup device moved to temporary paging space.

shrinkps: Paging space hd# removed.

shrinkps: Paging space hd# recreated with new si&e.

$o!e:Thechps -dcommand will prevent you from decreasing the si&e of hd# below ?; <B or

actually deleting it.

Mo%ing !he hd& paging space !o ano!her %olue group:

<oving a paging space with the name hd# from rootvg to another volume group is not

recommended, because the name is hard3coded in several places.

Mo%ing a paging space wi!hin !he sae '(:

/ommand used to move the default "hd#$ paging space from hdisk% to hdisk: within same

vg'

# igra!ep% -l hd& hdisk) hdisk*

I! !ake few inu!es depending upon !he si+e of eory

$o!e: <oving a paging space "including hd#$ from the default location to a different disk

within the same volume group does not reuire system reboot.

Reo%ing paging space ,no! hd&:

To remove a paging space, you have to deactivate the paging space.

=ou can use the swapoff command, which deactivates paging spaces without a reboot.

> swapoff @evice*ame @evice*ame C

Dg' > swapoff 0dev0paging%?

(mportant'Paging space need to be similar in si&e as give in below diagram.

Dup:

• %our system #enerates a system dump !hen a se&ere error occurs.

• 'ystem dumps can also (e user)initiate* (y users !ith root user authority.A system dump creates a +icture of your system,s memory contents.

• 'ystem a*ministrators an* +ro#rammers can #enerate a dump an*analy-e its contents !hen *e(u##in# ne! a++lications.



.onfigure a dup de%ice:

!hen you install the operating system, the dup device is automatically configured for you.

By default, the primary device is /de%/hd&, which is a paging logical volume, and the

secondary device is/de%/sysdupnull

A primary dup device is a dedicated dup device, while a secondary dup device is

shared. The dup device can be configured to either tape or a logical volume on the hard

disk to store the system dup.

$o!e: :.(f you use a paging device for dup devices only use hd#

(f you use a removable device, tape or @6@ be aware that the dup does not span

volumesE thus, the dup must fit on a single volume.

. (f your system has 4 7B or more of memory, then the default dup device is0dev0lgF duplv, and is a dedicated dup device.

.oand:

sysdupde%:-

The sysdupdev command changes the primary or secondary dup device designation in a

system that is running.

0o lis! !he curren! dup des!ina!ion :

# sysdupde% -l

/ommand to change the primary dup device from 0dev0hd# to the logical volume

0dev0dupdev'

# sysdupde% -P -p /de%/dupde%

De!erining !he si+e of a dup de%ice :

The si&e reuired for a dup is not a constant value, because the system does not dup

paging spaceE only data that resides in real memory can be duped. Paging space logical

volumes will generally hold the system dup.

!hen a system dup occurs, all of the kernel segment that resides in real memory is

duped "the kernel segment is segment %$. <emory resident user data "such as u3blocks$ are

also duped.

The minimum si&e for the dup space can best be determined using command sysdupdev

3e.



or production systems, it is a good practice to set the si&e of the dup logical volume to

;7B and above.

$o!e: (f you have confirmed that your dup device type is sysdup, use the extendlv

command to increase the space available.

.oand:

# sysdupde% -e

%49?3%4: Dstimated dup si&e in bytes' :;%9G#;4%

" The si&e of the dup device should be at least :;%9G#;4H bytes or ::9 <B.$

1!ar! a sys!e dup:

The dup can either be system initiated or user initiated.

By pressing AltI/trlI: or AltI/trlI; "Key euence$ or by using <(T utility dups can

be generated.

1ys!e ini!ia!ed dup:

(f your system stops with an GGG number flashing in the operator panel display, the system

has generated a dup and saved it to a primary dup device.

5erform the following steps to record the information contained in the GGG seuence

message'

1. ait until the /// se$uence *is+lays.

2. 0ecor* in se$uence e&ery co*e *is+laye* after the ///. n systems !itha ")*i#it or a 4)*i#it o+erator +anel you may nee* to +ress the reset(utton to &ie! the a**itional *i#its after the ///. 'ome systems use ana*&ance (utton to +erform this tas or the increment an* *ecrement(uttons.

". 'to+ recor*in# !hen the /// rea++ears.

Jikewise' :. 5ress reset or increment0decrement buttons

888 (Flashing)

132 Ist &alueIn*icates an Une+ecte*

'ystem 7alt

Mmm 2n* &alue In*icates the 8ause

of 7alt 80A'7 8D9

style:;font)family< =>i(eration 'erif,



serif?;@*** "r* &alue( Indicates the

Dump status DUMP CODE)

/// "r* &alue

ig. : GGG Drror lashing

.rash codes:

The crash codes that follow are part a Type :%; message.they are categori&ed in three ways'

* .a!egory* Begin the problem determination with software support.

2 .a!egory2 Begin the problem determination process with hardware support.

.a!egory Both software and hardware support may be needed in problem

determination.

1ys!e Dups .ode:

8o*e Descri+tion

3c3 Dump com+lete* successfully.

3c2 Dump starte*.

3c"t*@he dump is inhi(ite*.

3c4 Dump com+lete* unsuccessfully. Not

enou#h s+ace a&aila(le on dump *e&ice.

Partial dump a&aila(le.

3c5 Dump faile* to start. Une+ecte* error

occurre* !hen attem+tin# to !rite to dump

*e&ice.

3cC Net!or dump in +ro#ress.

3c/ Dump *isa(le*. 'ystem con#uration *oes

not inclu*e a dump *e&ice.

3cE 'ystem initiate* dump starte*.

!hen the system dup completes, the system either halts or reboots, depending upon the

setting of the auto restart attribute of sys%.

# lsa!!r -3l sys) -a au!ores!ar!

autorestart true Automatically LDBMMT system after a crash True.

=ou can change this setting by typing the following command.



# chde% -l sys) -a au!ores!ar!4false

sys% changed


autorestart false Automatically LDBMMT system after a crash True.

5ser ini!ia!ed dup:

tarting a dup from the command line 3

(f you initiate the system dup from the command line, use the sysdupstart command with

a 3p flag to write to the primary device or a 3s flag to write to the secondary device.

# sysdups!ar! -p or -s

tarting a dup from the physical control panel 3

(f an N</ is not connected to your system, you can initiate a system dup by using the

physical control panel.

*ote ' =ou can use the physical control panel to perform functions such as (5J, power on,

and power off.

!here,A O2 5ower button

B O2 M*0M power symbol

/ O2 Type and serial number label

@ O2 unction0data display

D O2 erial port : connector

O2 5ower on light

A blinking light indicates standby power to the unit.

A constant light indicates full system power to the unit.

7 O2 ystem attention light

N O2 @ecrement button

( O2 Dnter button



P O2 (ncrement button

tarting a dup using special key seuences3

=ou can initiate a dup using the following special key seuences

• 8trl)Alt)NumPa*1 to !rite to the +rimary dump *e&ice.

• 8trl)Alt)NumPa*2 to !rite to the secon*ary dump *e&ice.

By default, the system will not begin a dup by pressing the special key seuences. To

enable dups via the use of the special key seuences, type

.oand:

sysdupde% -6

1!ar!ing a dup fro !he 7M. -

• n the 7M8 console choose the +artition you !ant to dump an* +ressthe ri#ht mouse (utton.

• 'elect 0estart Partition an* clic the left mouse (utton? a ne! screena++ears.'creen !ill a++ear as #i&en (elo! in #."

• 'elect Dump an* clic the F (utton to start the dump.

.opile and copy 1ys!e Infoa!ion:

• he sna+ comman* is use* to #ather con#uration information of thesystem.

• It +ro&i*es a con&enient metho* of sen*in# the lsl++ an* err+t out+ut toyour ser&ice su++ort center.

• It #athers the information an* com+resses the information to a +a le. he le may then (e !ritten to a *e&ice such as ta+e or DD ortransmitte* to a remote system.

• he information #athere* !ith the sna+ comman* mi#ht (e re$uire* toi*entify an* resol&e system +ro(lems.

.oand:

> snap 3a 3o 0dev0rmt%

> 0usr0sbin0snap 3gfk@ 3o 0dev0rmt%



Mptions' -c /ompress

-f ile system

-D 7athers dup and 0unix information. The primary dup device is used.

-g 7athers the output of the lslpp 3hac

-k 7athers kernel information.

-! *etwork related issue "T/50(5$

Before executing the snap 3c or snap 3o commands, any additional information reuired by

your service support center should be copied to the 0tmp0ibmsupt directory.

(f you intend to use a tape to send a snap image to (B< for software support, the tape must beone of the following formats'

• / mm 2." GB ca+acity

• / mm 5.3 GB ca+acity

• 4 mm 4.3 GB ca+acity

1ys!e Dup 8nalysis:

The kdb command interprets and formats control structures in the system and providesmiscellaneous functions for examining a dup. This command allows you to examine a

system dup or a running kernel.

.oand 1yn!a9 '

kdb flags; 1ys!eIage<ile 6ernel<ile 6ernelModule ;;;

1ys!eIage<ile = it contains system image

6ernel <ile = The Kernel file parameter specifies the A(Q 9J kernel that kdb will use to

resolve kernel symbol definitions. A kernel file must be available. !hen examining a system

dup, it is imperative that the kernel file be the same as the kernel that was used to take the

system dup. The default for the Kernel ile is 0unix.

6ernelModule = (t contains the file names of any additional kernel that the kdb command

uses modules and which are not found in kernel

Dg'3



# kdb /%ar/ad/ras/%core) /uni9

$o!e:the kernel file specified on the command line need to be the same kernel file that was

running at the time the system dupwas created.

Paging space:







paging. This type of logical volume is referred to as a paging space logical volume or simplypaging space.




other activities.







". If real memory is #reater than or e$ual to 256 MB paging space is 512

MB.

Low paging space:





)*ot enough memory+














parameter.

# lsps -a





including hd#.

> chps 3s ? hd#






> chps 3d : hd#

"/P














vg'











Dup:

















.oand:

sysdupde%:-




# sysdupde% -l


0dev0dupdev'








also duped.


3e.




;7B and above.



.oand:

# sysdupde% -e



1!ar! a sys!e dup:



be generated.





message'





888 (Flashing)


'ystem 7alt


of 7alt 80A'7 8D9






/// "r* &alue


.rash codes:





determination.

1ys!e Dups .ode:

8o*e Descri+tion


3c2 Dump starte*.







*e&ice.













sys% changed



5ser ini!ia!ed dup:









and power off.






O2 5ower on light





( O2 Dnter button










.oand:

sysdupde% -6










.oand:






-f ile system











1ys!e Dup 8nalysis:



.oand 1yn!a9 '









Dg'3





running at the time the system dupwas created.

Paging space:







paging. This type of logical volume is referred to as a paging space logical volume or simplypaging space.




other activities.







". If real memory is #reater than or e$ual to 256 MB paging space is 512

MB.

Low paging space:





)*ot enough memory+