[PERFORMANCE] how to set wal_buffers

Hi,

Our fine manual says:
"""
The amount of memory used in shared memory for WAL data. The default
is 64 kilobytes (64kB). The setting need only be large enough to hold
the amount of WAL data generated by one typical transaction, since the
data is written out to disk at every transaction commit. This
parameter can only be set at server start.
"""

but how can measure "one typical transaction"? i read in the archives
that the useful top for this parameter is 1MB is that an "oficial"
opinion?
while we are there is there any way to know how many transactions are
we processing per period of time?

--
Atentamente,
Jaime Casanova
Soporte y capacitación de PostgreSQL
Asesoría y desarrollo de sistemas
Guayaquil - Ecuador
Cel. +59387171157