Performance problems

Hello all,

I've a little performance problem with psql 7.2.3.

I have a little database with approx. eight tables. They have two or six
columns and less than 2000 rows.

Three of them are regularly updated by a small C++-tool. It inserts or
updates entries of these three tables. All entries of one of these
tables are deleted with "Delete from..." everytime the tools runs (e.g.
every 20 minutes).

I'm using indices on all tables.

Now I can observe the following phenomenon:

The total runtime of the tool is increasing up to a certain peak and
then it drops to the half of the peak.
The time interval from one peak to the next is also increasing as well
as the total value of the peak.

But the total time for database access is not only increasing for write
access but also for read access.

The time it takes to Select things from the database is increasing too.

I unfortunately don't understand the whole thing totally, but if I dump
the database (with pg_dump), delete it and restore it, the time values
for reading and writing have decreased to a normal level and begin to
increase again.

It seems to me, that I do sth. fundamentally wrong :( But even after
searching google and the postgresql archives I don't see the light at
all...

Please help me out here.

Thanks and best regards

Marco Wedekind