[Coco] Segment List Full on backup

[Allen Huffman]

> On Jan 27, 2015, at 5:19 AM, Gene Heskett <gheskett at wdtv.com> wrote:
> 
> On Tuesday 27 January 2015 00:48:27 Allen Huffman did opine
> And Gene did reply:
>> Er, how is it possible that backup can give a #217 error? I thought it
>> was cloning sector by sector, so what would segment lists have to do
>> with it?
> 
> You are using another fd.seg entry for every it.sas 
> sector*bytes_per_sector. An it.sas setting of 8 is only 2k.
> 
> There is room for only 48 entries of the 5 byte fd.seg's in the fd.sector 
> and it is not extensible.  So a file being copied will fill the fd.sector 
> at 2k+48=96 kilobytes.
> 
> If the disk is well used, the parts of the file may be widely scattered 
> (fragmented) on the disk.

Always useful information (like explaining the difference between #237 memory full and #207 out of memory) -- but "backup" shouldn't be touching the bitmap. It should just be cloning sector to sector, shouldn't it?

While I can't explain backup's behavior, I think I have an idea of what happened. In my most recent case, I had an MM/1 OSK disk (512-byte sectors, so every two LSNs on CoCo OS-9 represents one OSK sector). Since the EZ135 disks are 128MB (or 135MB is you use Segates "1K is 1000" marketting math), the LSN0 size is shown as $040000. I byte tapped that to $07FFFF (yeah, missing a sector) so OS-9/6809 could "see" the full disk. Before, backup only copied $040000 sectors (half the disk) because OS-9 read LSN0 and set the size to that (correct size if the sectors were 512 bytes).

Backup ran for hours and failed with a #217, so I wrote a BASIC09 program to read 256 bytes at a time from source to destination. It ran for hours, and got to the final sector (524287 or something) and then issues #217.

I think RBF is returning it because the sector exceeds the number of clusters that the DAM ($FFFF * 8 = 524,280) supports.

That's my current theory. The MM/1 disk wasn't maxed so even though I may not be able to get the very last few sectors via CoCo OS-9, I got all the data I was after.

		-- A