[log in to unmask] (jockc) wrote:
 
>I'm trying to understand the difference between DBCLOSE mode 2 and
>mode 3.. The manual says mode 2 close the dataset but mode 3 doesn't,
>but I'm not sure exactly what closing the dataset does aside from
>releasing some resources..
 
>I'm asking this because I'm working on some Image emulation routines
>for Unix and trying to get DBCLOSE to work right..
 
>Can any image wizards give me a clue here?
 
>tia
>[log in to unmask]
>--
i won't pretend to call myself a 'wizard' :-) but i think i can answer
your question.  the difference between mode2 and 3 has to do
with the data item list that dbget uses.  a common technique is
to replace 'all list' (@;) with 'star list' (*;) after the first dbget
call is made to a given data set.  the 'star list' tells image to
*reuse* the data item list (created during the first call) rather
than to rebuild (and keep rebuilding and keep rebuilding...) the
list every time a dbget call is made to that set.  soooo - a dbclose
mode2 tells image to 'forget' the list while mode3 retains the list.
other than that (not that it's trivial) the 2 dbclose calls are the
same (they 'rewind' the data set and release any locks).  trusting
that i'm reasonably accurate :-}      - donna