Re: Positioning the Cursor, from the Toolbox

["Joe Sam Shirah" <joe_sam@xxxxxxxxxxxxx>]

    Hi JHHL,

    Given the thunderous response so far, I'd say for a definitive answer
you'd have to try it yourself.

    However, my understanding is that your assumption regarding
sequential-by-key access is incorrect.  In the KeyedFile javadoc it says
"Access the records in an AS/400 file sequentially or by key."  Secondly,
note that the methods you refer to come from AS400File and are not
overridden in KeyedFile.  My conclusion is that those methods ignore the
keys and just read sequentially.

    Given your scenario of read, process, delete, if I were going to use RLA
( and I wouldn't - no flame or arguments, please.  Others would, I'm sure. )
it appears that one of the read() methods that use searchType would be the
way to go.  I'd expect you could set the key to zero and searchType to
KEY_GT to get what you want.

    One thing to be wary of with KeyedFile is this little gem:

Record-Level Access performance tips

Keyed access.  Do not use a KeyedFile when you can get away with using a
SequentialFile. Opening a physical file for keyed access is slower since the
database will order the file by key at the time of the open. If you don't
need any of the key functionality, just use a SequentialFile object.

at:

http://www-03.ibm.com/servers/eserver/iseries/toolbox/perfhints.html

    That seems odd to me, and I don't know anything about it other than what
it says, but I'd certainly check it out.

    HTH,
                                                         Joe Sam

Joe Sam Shirah -        http://www.conceptgo.com
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----- Original Message ----- 
From: "James H H Lampert" <jamesl@xxxxxxxxxxx>
To: <java400-l@xxxxxxxxxxxx>
Sent: Tuesday, August 29, 2006 1:55 PM
Subject: Positioning the Cursor, from the Toolbox


> Any Toolbox gurus out there?
>
> Do the cursor-positioning methods in the AS400File class,
> i.e., positionCursorBeforeFirst(),
> positionCursorToFirst(), and so forth, and the sequential
> reading methods, readFirst(), readNext(), and so forth,
> produce expected results if applied to a KeyedFile?
> Particularly a KeyedFile that's open on a physical file
> that is set to re-use deleted records?
>
> Scenario:
> Records are constantly being added to a file, FOO, by any
> number of jobs throughout the system. This file is being
> polled continuously, and records are being read, in FIFO
> order, copied into another file, BAR, and deleted from
> FOO, as fast as the polling job, FROBOZZ, can process
> them. If FROBOZZ opens FOO with the SequentialFile class,
> then FOO cannot re-use its deleted records, because if
> FIFO order would not be guaranteed if at any point FOO
> contains more than one active record. Thus, FROBOZZ, and
> all the jobs pouring records into FOO, would have to be
> shut down periodically to do a RGZPFM on FOO, or FOO would
> eventually overflow.
>
> FOO is, however, keyed uniquely on a rather long (i.e.,
> 21-digit!) numeric field that is incremented with each
> write operation. If we open it using the KeyedFile class,
> would I be correct in assuming that the aforementioned
> AS400File methods give us sequential-by-key access?
>
> --
> JHHL
> --