Scratch vs. Clearing System ASP (Deleting ASP Data)

We occasionally get questions from people in the field when doing previous-release-to-current-release migrations and following checklist "Restoring previous release user data to a new system: Step-by-step instructions" of Chapter 14 (Release-to-Release Support) of the Backup and Recovery manual. This checklist has you scratch the target system if it comes fully preloaded with LPPs.

The question is this: Is it OK to clear the system ASP instead of installing LIC and initializing and reconfiguring DASD, or can this cause problems later? What are the differences and risks of clearing the system ASP vs. scratch?

Why is this a big deal? Because deleting ASP data is MUCH faster than initializing and having to re-configure DASD.

Based on response from development, if the user is going to be creating user ASPs and/or IASPs, it is probably just as fast to re-initialize, install LIC and then reconfigure the disks instead of clearing the system ASP, removing units from the system ASP, and adding those units to a User ASP or IASP. If the original system has only a System ASP, and the target system will only have a system ASP, then the Install LIC and adding the disk units to the configuration is time that is not well spent.

While the function to clear ASP takes a very short time, storage recovery after the clear can take many hours. Each storage extent must be recovered. This can be reduced by deleting as many libraries/objects as possible prior to clearing the ASP. For example: DR testing found it took 12 hours to initialize the disks, another 12 hours to configure the disks back into the ASP. On a second test the ASP was cleared. Storage recovery took 6 hours. When considering if Scratch or Clearing ASP is the better option, the time savings for clearing the ASP should be tempered by the storage recovery time.

There is another reason why they might want to do the Install LIC and initialize the system and then add the disk units, even though it takes more time. When the System ASP is cleared, the old data is not totally wiped off of the pages of the disk units - just the first page of each extent is zeroed. So, most of the data is actually still physically on the disk units, but is inaccessible by a virtual address because the first page of the extent has been wiped out.

There are people who can use various disk tools to examine the raw disk pages - The data cannot be accessed via the virtual address because the virtual address is destroyed when the first page of the extent is cleared as part of the function of 'Deleting Asp Data'. The data for most of the extent is still physically on the disk pages - It is possible to scroll through that information. If people want it really erased and zeroed, then doing the install LIC and initialize system and reconfigure the disk configuration is the way to go.
 

Warning: Do not use this procedure if the reason for a scratch is due to damage, bad disk pages, or DASD/cache hardware errors - clearing the ASP opens up a potential to run into these problems later. Also, most of the data remains physically on disk, so this is not a secure way of erasing data from the system.

Steps to delete ASP data:

Steps to delete ASP data:

1) Perform a B Manual IPL to get to "IPL or Install the System" screen
2) Option 3 (Use Dedicated Service Tools - DST)
3) Option 4 (Work with disk units)
4) Option 1 (Work with disk configuration)
5) Option 3 (Work with ASP configuration)
6) Option 4 (Delete ASP data)
7) Option 4 to Select the ASP (that you want to delete) and Confirm this function
8) Exit DST back to the "IPL or Install the System" screen.

Note: Mirroring and Raid Striping will survive the deleting of the ASP data

Related document:  Steps for Clearing the System ASP