IBMi.org – Bart's blog

IBM i and PowerVM features and tools

Recovering an invalided Load Source disk

As I wrote in the previous post, there might a situation when another/former load source disk become part of the LPAR configuration. IBMi OS configuration allows to run only with one valid load source, therefore the operating system will change a specific sector, making a former load source disk a regular disk. Therefore, this disk can’t be used as the Load Source never again. In this post I will describe what sector need to be changed in order to recover the disk, and reuse it in another configuration.

Not sure if everyone has understood the idea, because I don’t think it may happen to a regular user. The procedure might be extremely helpful for people juggle with disks. For instance, cloning the OS, moving to another storage array, etc. To better explain the possible scenario, let’s imagine  the LPAR with one disk controller (NPIV/vSCSI/native attached) which is attaching few disks, one of these disk is obviously the Load Source (let’s call this disk – Disk A). Secondly, a new disk controller is added to the LPAR configuration. This controller connects the new storage array. Now, you are going to copy the Load Source from ‘old array’ to a disk on the new array (copying Disk A to Disk B). Once the copy process finish successfully, the Disk B is used for booting, and Disk A reports in the systems as Non-configured. Technically Disk A cannot be used as the Load Source anymore. Even if the disk controller pointing to the new array will be removed, and only original connection remains. IPL process will result in B2003145 LP=00036 code saying No valid Load Source found.

Using the procedure below you can recover the Disk A and use it as the Load Source again.

Keep in mind that this is low level operation. I’m not taking any responsibility for destroying the data.

First of all, double check that the former Load Source wasn’t added to the ASP configuration. The adding procedure performs a disk format and destroy the data.

In order to modify the boot sector. IPL the system in Manual mode, and open the DST menu, go to opt4 – Work with disk units , opt2  – Work with disk unit recovery, opt6 – Disk unit problem recovery procedures, opt2 – Display/change page data and select with option 1 against the former Load Source disk.

This screen illustrates Display/change disk menu, where disk with SN #YPKGVZ7BMTPS is the new Load Source and disk #50-0xxx is the former LS. Take option 1 against disk #50-0xxx, and display page 00000000.

When page 00000000 is displayed, you should see the similar result

Now, overwrite first two bits to C9, as shown below and press F9 to save the data.

That’s it, Shut down the LPAR. Remove the disk controller pointing to Disk B (new array), and try to boot from Disk A. If everything works well, you should see similar screen.

Just press F10 and accept the problem. I hope the OS will start again from ‘invalided’ Load Source disk :). You will not see the error within next IPL.

Good luck.

P.S If you still do not understand where the process can be used, leave me a comment. I will try to describe process differently.

 

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