From the manual pages (-- download them from IBPhoenix and search on
keyword 'multigenerational'):


MULTIGENERATIONAL ARCHITECTURE:

Server maintains older versions of records (as needed) so that
transactions can see a consistent view of data.

InterBase provides expedient handling of time-critical transactions
through support of data concurrency and consistency in mixed use --
query and update -- environments.

InterBase uses a multigenerational architecture, which creates and
stores multiple versions of each data record. By creating a new
version of a record, InterBase allows all clients to read a version
of any record at any time, even if another user is changing that
record. InterBase also uses transactions to isolate groups of
database changes from other changes.

OVERVIEW OF SWEEPING:

InterBase uses a multigenerational architecture. This means that
multiple versions of data records are stored directly on the data
pages. When a record is updated or deleted, InterBase keeps a copy
of the old state of the record and creates a new version. This can
increase the size of a database.

To limit the growth of the database, InterBase performs garbage
collection by sweeping the database. This process frees up space
allocated to outdated record versions. Whenever a transaction
accesses a record, outdated versions of that record are garbage
collected. Records that were rolled back are not be garbage
collected. To guarantee that all records are garbage collected,
including those that were rolled back, InterBase periodically
sweeps the database.



--- In firebird-support@yahoogroups.com, "drstanl" <drstanl@v...>
wrote:

> Thanks, Ali, for your corrections and particularly for your
> explanation. I've not heard of "MGA architecture" and a Google
> produces a lot of noise. If it is something that can be explained
> (conceputally, at least) in a sentence or two, I'd be happy to be
> educated.
>
> PS -- yes, I believe that client is currently using something like
> Btrieve.
>
> -- Stan