how to optemize the database to make it smaller

[stinger2]

a general question

with time the database is growing too much which makes the maintenance and moving the site more difficult
so my question is
can we remove some unnecessary componants from it

like deleting all the PM and Pm text
deleting all log files
any other non essential parts ....to be rebuild again

just to make it more clear

for example
deleting PM as running this query
TRUNCATE TABLE pm
TRUNCATE TABLE pmtext
(answered in anoither thread)

i dont know though wether I should run these queries apart or as one

i mean
TRUNCATE TABLE pm

and hit run

then another query
TRUNCATE TABLE pmtext

or i paste both of them and excute as one as??