database size grows (even after vacuum (full and analyze))....

Hello all,

My subject has been discussed before. I've browsed through the archives
and did what I could understand (I'm doing "vaccum analyze" on each of
my tables every 30 minutes and "vacuum full" on each of the tables every
2 hour).

My database gets about 30 INSERTs per minute, about 60 UPDATEs per
minute and about 30 DELETEs per minute in a way that line counts tend to
stabilize. The test is done in such a way that I can asure a constant
average rate of INSERTs and the same average rate of DELETEs (after a
certain life time for each record).

Dispite this, the file system size still grows (at about 500KB in about
1000 minutes).

I've placed here a pdf file showing my situation. It shows that line
counts tend do stabilize. But pg data size slowlly increases (the sudden
drops are the result of vacuum full, time unit is 5 minutes).
http://robotica.estg.ipvc.pt/software/linux/dbsizes.pdf

Can anyone tell me if this is ok, or should I atend to this matter. My
system is supposed to work continuouslly without maintenance.

Thank you

joao