There is a bit map that is stored for each record in the PRIV file that
represents the detail dataset. I cannot remember if this is correct,
but a binary 0 means active, and a binary 1 means deleted. Usually, the
PRIV file is blocked, so that there are many entries in one physical
record - the bitmap must be large enough to hold one binary digit for
each entry in the physical, disk file record. There is no way to get to
these bitmaps or pointers unless you are using PRIV mode raw reading of
the files.
>>> "Denys Beauchemin" <[log in to unmask]> Wednesday,
November 22, 2006 12:37:44 PM >>>
I see. And exactly what is the mechanism used to record the "logical
flag"
used to indicate that an entry is deleted? In other words, where is
that
flag kept, physically, not logically?
Denys
-----Original Message-----
From: Wyell Grunwald [mailto:[log in to unmask]]
Sent: Wednesday, November 22, 2006 11:17 AM
To: [log in to unmask]; [log in to unmask]
Subject: RE: [HP3000-L] Adager question
Certainly ! When a DBDELETE call is made to a detail dataset, in
order
to save processing time, the entry is logically flagged as being
deleted, and any pointers to that entry are changed to bypass the
entry
in the chain. The entry is NOT physically deleted from the PRIV file
that represents that detail dataset. By performing a detail pack,
either with Adager, DBGenrl, or dbunload/dbload, the logically deleted
(flagged as being deleted) entries are physically removed, leaving
only
the active, live entries.
When adding entries to a detail dataset, a highwater mark is kept that
indicates the maximum number of entries in the dataset. For example
if
I add 1,000 entries and delete 100 afterwards, my highwater mark
remains
at 1,000 because that is the most number of entries ever in the detail
dataset. Adager, in the below case, is telling the user that you
cannot
change the capacity below 1,000 (the highwater), because there are
physically 1,000 entries in the file (100 are logically deleted, but
are
physically still there).
Wyell
>>> "Denys Beauchemin" <[log in to unmask]> Wednesday,
November 22, 2006 11:58:21 AM >>>
Wyell, can you explain what you mean by "deleted logically, but not
physically deleted," ? I love to learn more about IMAGE.
Denys
-----Original Message-----
From: HP-3000 Systems Discussion [mailto:[log in to unmask]] On
Behalf
Of Wyell Grunwald
Sent: Wednesday, November 22, 2006 9:44 AM
To: [log in to unmask]
Subject: Re: [HP3000-L] Adager question
You need to pack the detail dataset to remove entries in the dataset
that are marked as deleted logically, but not physically deleted, then
you can reduce the capacity.
Wyell
>>> John Bawden <[log in to unmask]> Wednesday, November 22, 2006
9:24:35 AM >>>
Wes,
Is it a detail dataset that you are trying to change?
If so, you cannot make the capacity less than the high
water mark unless you first detpack the set.
--- "[log in to unmask]" <[log in to unmask]> wrote:
> Anyone know why when I try to change a dataset
> capacity in ADAGER it's telling me that the minimum
> acceptable capacity is higher than I'm trying to set
> it at?
> Present : 9763397
> New ?5500000
> The minimum acceptable capacity is 9763396
>
> Thanks,
> Wes
> Office 608-242-2712 x:1247
> Cell 608-556-0780
>
>
>
>
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John Bawden
Homestead3000 Consulting
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