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On 16 Apr 2013 13:23, Gqcy wrote:
<<SNIP>>
I would say that our goal (maybe misguided?) is:
_Slowly_ migrate away from the RLA programs, but attempt to
achieve benefits in performance (with page sizes, and Encoded
Vector Indexing on some of our files)..
PAGESIZE and EVI can be accomplished without converting any files. I
suggest converting applications to use the SQL for data access [thus
mitigating the effect of changing RcdFmt level identifiers for that
application], but leaving the files unchanged. Or convert the
applications to use the SQL for data access, and convert only specific
set of files to be created with SQL DDL according to whatever specific
reason justifies that action. That is, always *applications first*,
then *optionally* the database files as required.
Start with our Item master file, then our Bill of Materials file.
Why change them? Can one particular reason be articulated, other
than EVI and PAGESIZE which are already noted to be moot? The existing
files can have either or both, without changing from DDS to SQL.
I would delay any change until absolutely necessary. If by the time
that is necessary [e.g. a column with a data type supported only by SQL
is required], and if by then all applications referencing them have
since changed to use SQL, then there is no longer a concern about Record
Format level identifiers.
lots of our other big systems depend on multi-member files, so they
will need more like complete re-writes...
I have found that multi-member to single-member is sometimes not as
big an issue as first suspected, because the existing design of some
applications can be mostly unaffected. Often only the file maintenance
programs and the CL work that run before the actual application,
typically establishing the overrides to a specific member, are what need
to change. The code that effects the overrides can be replaced with an
OPNQRYF to generate a shared ODP, and close the ODP upon return.
Obviously not an option if the applications are already using some SQL
for data access.
The impact can be somewhat minimized with use of DDS LF and\or INDEX
with a WHERE clause to replace what they previously did with data in a
specific member. The logical is built over all of the data, now in one
member, in the altered PF for which the layout now has new field(s) on
which selection of the data is made specific to what was previously
accomplished by which member the application accessed for its data. The
DDS has the issue of the format requiring the new fields to be included,
and the SQL has the issue of [key] column ordering, but if the
applications were already designed with logical independence, then they
may be able to be changed easier than if not.
Regards, Chuck
midrange.com
