tuning for TPC-C benchmark

Hello all,
I'm doing tests on various Database and in particular I'm running a
comparison between Oracle 10g and Postgres 8.1 on a dedicated server
with 2 processors Dual-Core AMD Opteron 2218 2.6 GHz, 4GB of memory
and Debian GNU / Linux version 2.6.18-5. Performance is very similar up
to 30 users, but from 40 onwards with Postgres fall quickly. That is
not what happens with Oracle that comes to 600 users. Can you help me
with the tuning ?
Thanks a lot
My postgresql.conf configuration is:
#---------------------------------------------------------------------------
# FILE LOCATIONS
#---------------------------------------------------------------------------

# The default values of these variables are driven from the -D command
line
# switch or PGDATA environment variable, represented here as
ConfigDir.

#data_directory = 'ConfigDir' # use data in another
directory
hba_file = '/etc/postgresql/8.1/main/pg_hba.conf' # host-based
authentication file
ident_file = '/etc/postgresql/8.1/main/pg_ident.conf' # IDENT
configuration file

# If external_pid_file is not explicitly set, no extra pid file is
written.
external_pid_file = '/var/run/postgresql/8.1-main.pid' #
write an extra pid file

#---------------------------------------------------------------------------
# CONNECTIONS AND AUTHENTICATION
#---------------------------------------------------------------------------

# - Connection Settings -

#listen_addresses = 'localhost' # what IP address(es) to
listen on;
# comma-
separated list of addresses;
# defaults to
'localhost', '*' = all
listen_addresses = '*'
port = 5432
max_connections = 220
# note: increasing max_connections costs ~400 bytes of shared memory
per
# connection slot, plus lock space (see max_locks_per_transaction).
You
# might also need to raise shared_buffers to support more connections.
#superuser_reserved_connections = 2
unix_socket_directory = '/var/run/postgresql'
#unix_socket_group = ''
#unix_socket_permissions = 0777 # octal
#bonjour_name = '' # defaults to the computer
name

# - Security & Authentication -

#authentication_timeout = 60 # 1-600, in seconds
ssl = true
#password_encryption = on
#db_user_namespace = off

# Kerberos
#krb_server_keyfile = ''
#krb_srvname = 'postgres'
#krb_server_hostname = '' # empty string matches any
keytab entry
#krb_caseins_users = off

# - TCP Keepalives -
# see 'man 7 tcp' for details

#tcp_keepalives_idle = 0 # TCP_KEEPIDLE, in seconds;
# 0 selects the
system default
#tcp_keepalives_interval = 0 # TCP_KEEPINTVL, in seconds;
# 0 selects
the system default
#tcp_keepalives_count = 0 # TCP_KEEPCNT;
# 0 selects
the system default

#---------------------------------------------------------------------------
# RESOURCE USAGE (except WAL)
#---------------------------------------------------------------------------

# - Memory -

shared_buffers = 49152 # min 16 or max_connections*2,
8KB each, 384MB
temp_buffers = 1000 # min 100, 8KB each
max_prepared_transactions = 350 # can be 0 or more
# note: increasing max_prepared_transactions costs ~600 bytes of
shared memory
# per transaction slot, plus lock space (see
max_locks_per_transaction).
work_mem = 1024 # min 64, size in
KB
maintenance_work_mem = 524288 # min 1024, size in KB, -512
MB-
max_stack_depth = 6144 # min 100, size in KB

# - Free Space Map -
max_fsm_pages = 58000 # min max_fsm_relations*16, 6
bytes each
max_fsm_relations = 3000 # min 100, ~70 bytes each

# - Kernel Resource Usage -

#max_files_per_process = 1000 # min 25
#preload_libraries = ''

# - Cost-Based Vacuum Delay -

#vacuum_cost_delay = 0 # 0-1000 milliseconds
#vacuum_cost_page_hit = 1 # 0-10000 credits
#vacuum_cost_page_miss = 10 # 0-10000 credits
#vacuum_cost_page_dirty = 20 # 0-10000 credits
#vacuum_cost_limit = 200 # 0-10000 credits

# - Background writer -

#bgwriter_delay = 5000 # 10-10000 milliseconds
between rounds
bgwriter_lru_percent = 0 # 0-100% of LRU buffers
scanned/round
bgwriter_lru_maxpages = 0 # 0-1000 buffers max
written/round
bgwriter_all_percent = 0 # 0-100% of all buffers
scanned/round
bgwriter_all_maxpages = 0 # 0-1000 buffers max
written/round

#---------------------------------------------------------------------------
# WRITE AHEAD LOG
#---------------------------------------------------------------------------

# - Settings -

fsync = off # turns forced synchronization
on or off
#wal_sync_method = fsync # the default is the first
option
# supported by the operating
system:
# open_datasync
# fdatasync
# fsync
# fsync_writethrough
# open_sync
#full_page_writes = on # recover from partial page
writes
#wal_buffers = 8 # min 4, 8KB each
#commit_delay = 5 # range 0-100000, in
microseconds
#commit_siblings = 5 # range 1-1000
# - Checkpoints -

checkpoint_segments = 100 # in logfile segments, min 1,
16MB each
checkpoint_timeout = 1800 # range 30-3600, in seconds
#checkpoint_warning = 30 # in seconds, 0 is off

# - Archiving -

#archive_command = '' # command to use to archive a
logfile
# segment

#---------------------------------------------------------------------------
# QUERY TUNING
#---------------------------------------------------------------------------

# - Planner Method Configuration -

#enable_bitmapscan = on
#enable_hashagg = on
#enable_hashjoin = on
#enable_indexscan = on
#enable_mergejoin = on
#enable_nestloop = on
#enable_seqscan = on
#enable_sort = on
#enable_tidscan = on

# - Planner Cost Constants -

effective_cache_size = 196608 # typically 8KB each
#random_page_cost = 4 # units are one sequential
page fetch
# cost
#cpu_tuple_cost = 0.01 # (same)
#cpu_index_tuple_cost = 0.001 # (same)
#cpu_operator_cost = 0.0025 # (same)

# - Genetic Query Optimizer -

#geqo = on
#geqo_threshold = 12
#geqo_effort = 5 # range 1-10
#geqo_pool_size = 0 # selects default based on
effort
#geqo_generations = 0 # selects default based on
effort
#geqo_selection_bias = 2.0 # range 1.5-2.0

# - Other Planner Options -

#default_statistics_target = 10 # range 1-1000
#constraint_exclusion = off
#from_collapse_limit = 8
#join_collapse_limit = 8 # 1 disables collapsing of
explicit
# JOINs

#---------------------------------------------------------------------------
# ERROR REPORTING AND LOGGING
#---------------------------------------------------------------------------

# - Where to Log -

#log_destination = 'stderr' # Valid values are
combinations of
# stderr, syslog and eventlog,
# depending on platform.

# This is used when logging to stderr:
#redirect_stderr = off # Enable capturing of stderr
into log
# files

# These are only used if redirect_stderr is on:
#log_directory = 'pg_log' # Directory where log files
are written
# Can be absolute or relative
to PGDATA
#log_filename = 'postgresql-%Y-%m-%d_%H%M%S.log' # Log file name
pattern.
# Can include strftime()
escapes
#log_truncate_on_rotation = off # If on, any existing log file of the
same
# name as the new log file
will be
# truncated rather than
appended to. But
# such truncation only occurs
on
# time-driven rotation, not on
restarts
# or size-driven rotation.
Default is
# off, meaning append to
existing files
# in all cases.
#log_rotation_age = 1440 # Automatic rotation of
logfiles will
# happen after so many
minutes. 0 to
# disable.
#log_rotation_size = 10240 # Automatic rotation of
logfiles will
# happen after so many
kilobytes of log
# output. 0 to disable.
# These are relevant when logging to syslog:
#syslog_facility = 'LOCAL0'
#syslog_ident = 'postgres'

# - When to Log -

#client_min_messages = notice # Values, in order of
decreasing detail:
# debug5
# debug4
# debug3
# debug2
# debug1
# log
# notice
# warning
# error

#log_min_messages = notice # Values, in order of
decreasing detail:
# debug5
# debug4
# debug3
# debug2
# debug1
# info
# notice
# warning
# error
# log
# fatal
# panic

#log_error_verbosity = default # terse, default, or verbose
messages

#log_min_error_statement = panic # Values in order of
increasing severity:
# debug5
# debug4
# debug3
# debug2
# debug1
# info
# notice
# warning
# error
# panic(off)
#log_min_duration_statement = -1 # -1 is disabled, 0 logs all
statements
# and their durations, in
milliseconds.

#silent_mode = off # DO NOT USE without syslog or
# redirect_stderr

# - What to Log -

#debug_print_parse = off
#debug_print_rewritten = off
#debug_print_plan = off
#debug_pretty_print = off
#log_connections = off
#log_disconnections = off
#log_duration = off
log_line_prefix = '%t ' # Special values:
# %u = user name
# %d = database name
# %r = remote host and port
# %h = remote host
# %p = PID
# %t = timestamp (no
milliseconds)
# %m = timestamp with
milliseconds
# %i = command tag
# %c = session id
# %l = session line number
# %s = session start
timestamp
# %x = transaction id
# %q = stop here in non-
session
# processes
# %% = '%'
# e.g. '<%u%%%d> '
#log_statement = 'none' # none, mod, ddl, all
#log_hostname = off

#---------------------------------------------------------------------------
# RUNTIME STATISTICS
#---------------------------------------------------------------------------

# - Statistics Monitoring -

#log_parser_stats = off
#log_planner_stats = off
#log_executor_stats = off
#log_statement_stats = off

# - Query/Index Statistics Collector -

stats_start_collector = off
stats_command_string = off
stats_block_level = off
stats_row_level = off
stats_reset_on_server_start = off

#---------------------------------------------------------------------------
# AUTOVACUUM PARAMETERS
#---------------------------------------------------------------------------

autovacuum = off # enable autovacuum
subprocess?
#autovacuum_naptime = 60 # time between autovacuum
runs, in secs
#autovacuum_vacuum_threshold = 1000 # min # of tuple updates
before
# vacuum
#autovacuum_analyze_threshold = 500 # min # of tuple updates
before
# analyze

#autovacuum_vacuum_scale_factor = 0.4 # fraction of rel size before
# vacuum
#autovacuum_analyze_scale_factor = 0.2 # fraction of rel size before
# analyze
#autovacuum_vacuum_cost_delay = -1 # default vacuum cost delay
for
# autovac, -1 means use
# vacuum_cost_delay
#autovacuum_vacuum_cost_limit = -1 # default vacuum cost limit
for
# autovac, -1 means use
# vacuum_cost_limit

#---------------------------------------------------------------------------
# CLIENT CONNECTION DEFAULTS
#---------------------------------------------------------------------------

# - Statement Behavior -

#search_path = '$user,public' # schema names
#default_tablespace = '' # a tablespace name, '' uses
# the default
#check_function_bodies = on
#default_transaction_isolation = 'read committed'

#default_transaction_read_only = off
#statement_timeout = 0 # 0 is disabled, in
milliseconds

# - Locale and Formatting -

#datestyle = 'iso, mdy'
#timezone = unknown # actually, defaults to TZ
# environment setting
#australian_timezones = off
#extra_float_digits = 0 # min -15, max 2
#client_encoding = sql_ascii # actually, defaults to
database
# encoding

# These settings are initialized by initdb -- they might be changed
lc_messages = 'it_IT.UTF-8' # locale for system
error message
# strings
lc_monetary = 'it_IT.UTF-8' # locale for monetary
formatting
lc_numeric = 'it_IT.UTF-8' # locale for number
formatting
lc_time = 'it_IT.UTF-8' # locale for time
formatting

# - Other Defaults -

#explain_pretty_print = on
#dynamic_library_path = '$libdir'

#---------------------------------------------------------------------------
# LOCK MANAGEMENT
#---------------------------------------------------------------------------

#deadlock_timeout = 1000 # in milliseconds
#max_locks_per_transaction = 64 # min 10
# note: each lock table slot uses ~220 bytes of shared memory, and
there are
# max_locks_per_transaction * (max_connections +
max_prepared_transactions)
# lock table slots.

#---------------------------------------------------------------------------
# VERSION/PLATFORM COMPATIBILITY
#---------------------------------------------------------------------------

# - Previous Postgres Versions -

#add_missing_from = off
#backslash_quote = safe_encoding # on, off, or safe_encoding
#default_with_oids = off
#escape_string_warning = off
#regex_flavor = advanced # advanced, extended, or basic
#sql_inheritance = on

# - Other Platforms & Clients -

#transform_null_equals = off

#---------------------------------------------------------------------------
# CUSTOMIZED OPTIONS
#---------------------------------------------------------------------------

#custom_variable_classes = '' # list of custom variable
class names

________________________________________________
Tiscali Voce 8 Mega (Telefono+Adsl). Attiva entro il 22/11/07: chiami in tutta Italia e navighi SENZA LIMITI A SOLI 4,95€ AL MESE FINO AL 31/03/2008!
Dal 1° aprile 2008 paghi 28,95 € al mese.
http://abbonati.tiscali.it/telefono-adsl/prodotti/tc/voce8mega/