To activate powa-archvist on your PostgreSQL server, add 'powa' to the list of
shared_preload_libraries in $PGDATA/postgresql.conf:

shared_preload_libraries = 'pg_stat_statements,powa'
track_io_timing = on

Also, create the powa database and add extensions

createdb powa
psql -d powa -c "
CREATE EXTENSION pg_stat_statements;
CREATE EXTENSION btree_gist;
CREATE EXTENSION powa;
"

After this, restart postgresql to start the background worker.

See http://powa.readthedocs.org/en/latest/powa-archivist/installation.html#id1
for detailed installation instructions.

Optionally, but warmly recommended, is the use of databases/pg_qualstats and
databases/pg_stat_kcache together with powa.

Use the databases/powa-web port to visualize the data.