ipcs on UNIX

[#1]

Is anyone farmiliar with the ipcs command on UNIX. When you perform this command with a running SAP system,

you see a bunch of memory segments owned by <SID>adm, but one in particular is interesting,

you see a "D" in the permissions

m 294928 0x00000000 D-rw-rw-rw- ecdadm sapsys

Anyone farmiliar with what this is?

Thanks

[Former Member · Accepted solution]

Hi Jeremy,

The "man" pages on AIX says the following for mode 😧

"If the associated shared memory segment has been removed. It disappears when the last process attached to the segment detaches it."

I guess it means that an attached process has removed the segment but the system cannot delete the shared memory segment because at least one other process is still attached (using) that shared memory segment.

http://publib.boulder.ibm.com/infocenter/pseries/v5r3/index.jsp?topic=/com.ibm.aix.doc/cmds/aixcmds3...

Regards,

Gary

[Former Member]

Hello Jeremy,

Some additional general information that may be of interest to you.

Under MODE the D according to the 'ipcs' documentation "means that the associated shared memory segment has been removed. It will disappear when the last process attached to the segment detaches it".

When the mode of the ID you want to remove contains a D (i.e. D-rw-rw-rw-), it means the shared memory segment is already detached, you do not bother about it. It is analogous to a "<defunct>" process. You cannot remove a shared memory segment that is already detached (released).

It should be automatically deleted once the last process attached to it is completed. If it is staying for a long period, then the process might have become a runaway. The shared memory isn't removed until the last process detaches. (see 'man ipcrm').

Using 'ipcs -moba' to display all the shared memory information and then try to delete with ipcrm -m followed by the number. You would delete entries only for those with 0 under NATTACH in this case.

The entries with the D flag are not critical. They will disappear during the next reboot at the latest.

Regards, Mark

[Former Member]

Hello Jeremy,

Running 'ipcs -mob | grep m | grep ' on a test HP-UX system I get the following:

T ID KEY MODE OWNER GROUP NATTACH SEGSZ

Shared Memory:

m 24381 0x00000000 D-rw-rw-rw- h9cadm sapsys 12 536870912

This is not an issue but just the way that extended memory is managed at OS level. This is cleared when the instance is restarted and then created again after the next restart.

I hope this helps.

Regards, Mark

[Former Member]

Hi Jeremy,

Confirmation of my thoughts can be found on page 59 of the following PDF document:

http://www.commoncriteriaportal.org/public/files/epfiles/0194b.pdf

Regards,

Gary

[Former Member]

Thanks, It does help with the use of the tool. WHat I was looking for was more of an explanation of the output from an SAP perspective.

[Former Member]

Hi

I am giving some description about ICPS and i do hope this will help you to solve your problem.

ipcs - report inter-process communication facilities status

ipcs [-aAbcimopqst] [-D mtype]

DESCRIPTION

The ipcs utility prints information about active inter-process communication facilities. The information that is displayed is controlled by the options supplied.Without options, information is printed in short format for message queues, shared memory, and semaphores that are currently

active in the system.

OPTIONS ->

-D mtype -> Displays, in hexadecimal and ASCII, the contents of all messages of type mtype found on any message queue that the user invoking ipcs has permission to read. If mtype is 0, all messages are displayed. If mtype is negative, all messages with type less than or equal to the absolute value of mtype are displayed.(See msgrcv(2) and msgsnap(2)).

Thanks

Mrutyunjaya Tripathy