\db
    list tablespaces

pg_global
    $PGDATA/global
pg_default
    $PGDATA/base/dboid
others...
    $PGDATA/pg_tblspc/tsoid/<path-to-catalog>/ver/dboid

create tablespace <tbspname> to location '...';
create table ... tablespace <tbspname>;


pg_tablespace_size('<tbspname>')
pg_tablespace_databases('<tbspname>')