Re: teraspace, user spaces, etc.

[Dave McKenzie <davemck@xxxxxxxxxx>]

I'm including source for a tool that displays disk locations by virtual
address.  You can use it to find how an (up to 16 Meg) segment is scattered on
disk.

To use it you first use the SEGLOD cmd to build a copy of the Permanent
Directory, which is a machine index that maps virtual addresses to disk
addresses.  Then you use the SEGDSP cmd to display the disk extents (blocks of
contiguous disk sectors) that store address segments.

Instructions are in the source for the 2 cmds.

NOTE:  It only works on V4R4 and below.  For V4R5, IBM changed the Permanent
Directory from a simple machine index to a combination of a smaller machine
index and some memory tables.  A good example of the perils of knowing too much
about internal implementation details (or depending too much on that knowledge
:-)

--Dave


Alexei Pytel wrote:
> 
> Steve,
> you confuse two different things - virtual memory and auxiliary memory.
> 
> In a virtual memory two contiguous pages will have adjacent addresses.
> How it will be stored on a disk is entirely different matter - these pages
> may be contiguous or not, they even may be on different drives.
> It depends on many factors.

<snip>

Steve Richter wrote:
>
> so when a usrspc of say size 1 MB is created, 1MB of contiguous disk are
> set
> aside for it.
> If the size of the usrspc is extended to 2MB does this mean that the entire
> 1MB have to be moved to the new 2MB sized location?

Segdsp.zip