Informing the IBM Community

Tech tip: finding AIX’s save buttons


Green Save Button with pointing Hand Cursor

If there’s one thing that I will never get used to about Google Docs, it is that it doesn’t save your changes. Or rather, it does it for you.

Well, Mr Google, I want the “save” button back. Even if it doesn’t do anything.

There is something very consoling about a save button. It’s closure. It’s commitment. It’s a way of the computer saying: “your wish is my command!”, thus keeping  the relationship between humans and technology on the right footing.

If you have IBM Power Systems running AIX, you need to be aware that there is a save button, or at least a way of telling the computer: “I’ve changed something, I mean it to stay like that.”

Here are four places that you use something equivalent to a save button:

1. Changing devices

On the AIX command line, you may want to change some parameters for devices such as disks or network adapters. For the most part, these changes will be done using the chdev command.

However, if the device is in use (such as a disk that is in an active volume group), you will not be able to change the device settings immediately.

chdev –l hdisk0 –a queue_depth=16
Method error (/etc/methods/cfgdisk):
                  0514-062 Cannot perform the requested function because the specified device is busy.

In cases like this, you can add a flag to make the changes permanent. Add the –P flag to your command.

chdev –l hdisk0 –a queue_depth=16 –P

This setting will take effect from next time the system is rebooted.

2. Dynamic LPAR changes

Why reboot when you can make changes on the fly? With Dynamic LPAR you can assign more memory, processor capacity or devices to a logical partition. You do this via the Hardware Management Console (HMC) or, if you don’t have that, using Integrated Virtualization Manager (IVM).

The important thing is to save the current profile after you make any changes via DLPAR. If you don’t, the next time you shut down the partition and activate it again, you’ll be picking up the original profile without whatever changes you made using DLPAR.

Having an OS that is missing some of its memory or that can’t find the adapter for some of its disks can be pretty unpleasant. You can address that by a simple save current config in the HMC/IVM browser.

In fact, it’s a good idea to do a save current config before you shut down and start up an OS, even if you’re not aware of any changes via DLPAR since the last time the partition was activated.

3. AIX environmental variables

You can set environmental variables for your shell session. However, these changes will only last as long as your shell session is active. Once you disconnect, you’ve lost variables such as your TERM type (for keyboard layout), your shell prompt or your extended shell history.

The easiest solution, for the most part, is to add the variables you want to keep in the .profile file which is in your home directory (these instructions are applicable for the Korn shell).

For example, to add extended history:


Then you can use the following command to display the date and time stamp for the commands in your shell history:

fc –t

111     2015/07/15 09:03:27 :: fc –t

4. Operating system backups

You can back up the AIX operating system using the mksysb command. There are a few similar commands such as mkdvd, which writes the mksysb OS backup into a DVD format.

You will find plenty of documentation online about the mksysb command and if you ever lose your OS, you’ll be glad you’ve got a recent mksysb backup. Same goes for when you are making major changes, such as doing AIX upgrades or application patching.

It is always worth testing to make sure you have the procedures in place to restore from a mksysb backup. If you don’t have a backup at all, not even an old one, then you might be facing cloning the OS from some hopefully similar system, or building the whole thing from scratch.

There are many other ways that you can save your changes on AIX and in the Power Systems environment. It is important to keep this in mind, especially when you’re building a new system or if it is undergoing significant changes, perhaps due to some business project. It is the sort of knowledge that might just save you.

Having worked on IBM systems since 1991, Anthony English has seen how AIX and virtualisation can manage all kinds of business environments. He is a well-recognised author in the IT field and he writes about business systems improvement through his blog at Anthony is based in Sydney, Australia, with his wife and his seven children.

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