High consumns memory

I have a software developed in Delphi as a Windows Service, but, i don't
know why, it consumns an unexpected large system memory (1.3g).
The service access PostgresSQL by ODBC driver (psqlodbc_08_03_0400) and it
consist simply of a loop calling a procedure PL/PGSQL. How to discover what
is causing or why this high memory usage ? What objects are being used on
this session ?
Software developed in Delphi 7 as a windows service.
PostgresSQL 8.3.6 Database with PostGis extension

Server p52a
S.O.: Red Hat Enterprise Linux AS release 4 (Nahant Update 1)
linux 2.6.9-11.EL #1 SMP ppc64 ppc64 ppc64 GNU/Linux
S.O. information

Date 13/04/2009

top - 15:20:35 up 10 days, 14:22, 1 user, load average: 0.80, 0.66, 0.63
Tasks: 134 total, 2 running, 132 sleeping, 0 stopped, 0 zombie
Cpu(s): 3.2% us, 0.1% sy, 0.0% ni, 96.2% id, 0.3% wa, 0.1% hi, 0.1% si
Mem: 4107392k total, 1552168k used, 2555224k free, 10172k buffers
Swap: 2031608k total, 79740k used, 1951868k free, 1402644k cached

PID USER PR NI VIRT SWAP RES SHR DATA CODE S %CPU %MEM TIME+
COMMAND
1843 postgres 16 0 857m 664m 193m 186m 7120 3540 R 19.9 4.8 0:06.13
postgres: citgis citgis 10.255.100.73(1557) SELECT

Date 14/04/2009

top - 12:51:44 up 11 days, 11:54, 1 user, load average: 0.41, 0.45, 0.42
Tasks: 128 total, 1 running, 127 sleeping, 0 stopped, 0 zombie
Cpu(s): 3.8% us, 0.1% sy, 0.0% ni, 95.7% id, 0.2% wa, 0.1% hi, 0.0% si
Mem: 4107392k total, 4097504k used, 9888k free, 48252k buffers
Swap: 2031608k total, 62680k used, 1968928k free, 2804800k cached

PID USER PR NI VIRT SWAP RES SHR DATA CODE S %CPU %MEM TIME+
COMMAND
1843 postgres 15 0 1896m 114m 1.7g 737m 1.0g 3540 S 26.9 44.4 181:59.47
postgres: citgis citgis 10.255.100.73(1557) idle

As shown in column DATA(7120) on 03/04 and on 04/04 (1.0g) been a
significant increase in the consumption of memory.

postgresql.conf information:

name | setting |
unit
---------------------------------+--------------------------------------+------
archive_mode | on |
autovacuum_analyze_scale_factor | 0.4 |
autovacuum_analyze_threshold | 500 |
autovacuum_vacuum_threshold | 1000 |
checkpoint_segments | 15 |
checkpoint_timeout | 1800 | s
default_statistics_target | 50 |
effective_cache_size | 249600 |
8kB
fsync | on |
logging_collector | on |
maintenance_work_mem | 409600 |
kB
max_connections | 100 |
max_fsm_pages | 3458000 |
shared_buffers | 64000 |
8kB
wal_buffers | 100 |
8kB
work_mem | 5120 |
kB