[open-cobol-list] Re: [Tiny-cobol-users] ISAM replacement

[Bernard Giroud]

>From what I looked so far:

1) Yes, multiple keys with multiple segments with/without duplicates.
2) It emulates/is compatible with C-ISAM: so data in the .dat file and
indexes in the .idx file.
3) Yes, see 2 above.

Bernard Giroud
Credit Lyonnais (Suisse) SA
----- Original Message -----
From: "David Essex" <address@hidden>
To: "tiny-cobol-users" <address@hidden>
Sent: Tuesday, November 09, 2004 6:22 PM
Subject: Re: [Tiny-cobol-users] ISAM replacement



BTW, does any one know if VBISAM supports the following:

- Multiple keys with duplicates.
- Is the data and index stored in a single or different files.
- Can multiple keys indexes be stored in a single file.


Giroud, Bernard wrote:

> David Essex a écrit :
>
>> Andrew Cameron wrote:
>> ...
>> > The best way to do it would probably be a switch for the
>> > configure script so you Could choose to use either the old
>> > DB backend or the New VBISAM backend.
>>
>> Modifications to the 'configure script' should not be a problem.
>>
>> However removing BDB will not be easy for the following reasons.
>>
>> First, all types of file IO in the TC RTL use BDB.
>
> You mean: Indexed, Relative and Sort. But not Sequential nor Line
> sequential.
> And you can always implement a relative file by an indexed one with
numeric
> keys.

Actually all file types use the BDB structures.

So even if VBISAM where used just for INDEXED file types, the current
RTL sources would have to be decoupled from BDB.


>> The RTL can be
>> changed to optionally use BDB for only INDEXED file types. However this
>> is not a small change thus will require some work.
>>
>> Second, getting TC to work with VBISAM, for INDEXED file types, will
>> require an addition to the RTL. Again this will require some work.
>>
>> Third, BDB is used for the SORT statement to sort files. I do not think
>> that VBISAM provides a SORT facility. Even if it did it would require
>> some work on the RTL.
>>
> BDB is used implicitly: the additions in the file are arranged in sorted >
order,
> and then it is read again sequentially by the order of the keys. So, any
> ISAM method will work in this case.

If that is true, what is the advantage in duplicating the code just to
use VBISAM instead of BDB ?


> BTW, the sort should really be implemented by a sort, not an indexed
> file method.

I agree, but AFAIK no LGPL SORT utility exists.


>> Perhaps the best solution is not to think of VBISAM as a complete BDB
>> substitute, but as a optional substitute for INDEXED files.
>>
>> > One thing to note when you add an extension try to get it to work
>> > Under all the current platforms supported by TC.
>>
>> VBISAM is supposed to be OS independent, but it appears to have been
>> developed on UN*X. So until it can be compiled and run on Win32 without
>> a POSIX layer (using MinGW), I don not think it can be considered a
>> serious contender for BDB.
>>
> I agree this might be a problem.
>
>> Anyway, my 2 cent worth.



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