More AIX 5.3 fun - out of memory ?

Having successfully got pg 8.1.3 to run, I'm simply trying to pg_restore
a dump from our live server. However, even very soon into the restore, I
get these messages from the autovacuum daemon once per minute:

2006-03-28 14:15:35 BSTLOG:  autovacuum: processing database "laterooms"
TopMemoryContext: 50584 total in 6 blocks; 11112 free (13 chunks); 39472
used
TopTransactionContext: 8192 total in 1 blocks; 7688 free (10 chunks);
504 used
Operator class cache: 8192 total in 1 blocks; 4936 free (0 chunks); 3256
used
Autovacuum context: 122880 total in 4 blocks; 61472 free (17 chunks);
61408 used
smgr relation table: 8192 total in 1 blocks; 3904 free (0 chunks); 4288 used
Portal hash: 8192 total in 1 blocks; 5968 free (0 chunks); 2224 used
PortalMemory: 0 total in 0 blocks; 0 free (0 chunks); 0 used
Relcache by OID: 8192 total in 1 blocks; 1816 free (0 chunks); 6376 used
CacheMemoryContext: 516096 total in 6 blocks; 78480 free (0 chunks);
437616 used
pg_index_indrelid_index: 1024 total in 1 blocks; 392 free (0 chunks);
632 used
pg_attrdef_adrelid_adnum_index: 1024 total in 1 blocks; 328 free (0
chunks); 696 used
pg_autovacuum_vacrelid_index: 1024 total in 1 blocks; 392 free (0
chunks); 632 used
pg_type_typname_nsp_index: 1024 total in 1 blocks; 328 free (0 chunks);
696 used
pg_type_oid_index: 1024 total in 1 blocks; 392 free (0 chunks); 632 used
pg_trigger_tgrelid_tgname_index: 1024 total in 1 blocks; 328 free (0
chunks); 696 used
pg_statistic_relid_att_index: 1024 total in 1 blocks; 328 free (0
chunks); 696 used
pg_auth_members_member_role_index: 1024 total in 1 blocks; 328 free (0
chunks); 696 used
pg_auth_members_role_member_index: 1024 total in 1 blocks; 328 free (0
chunks); 696 used
pg_rewrite_rel_rulename_index: 1024 total in 1 blocks; 328 free (0
chunks); 696 used
pg_proc_proname_args_nsp_index: 1024 total in 1 blocks; 256 free (0
chunks); 768 used
pg_proc_oid_index: 1024 total in 1 blocks; 392 free (0 chunks); 632 used
pg_operator_oprname_l_r_n_index: 1024 total in 1 blocks; 192 free (0
chunks); 832 used
pg_operator_oid_index: 1024 total in 1 blocks; 392 free (0 chunks); 632 used
pg_opclass_oid_index: 1024 total in 1 blocks; 392 free (0 chunks); 632 used
pg_opclass_am_name_nsp_index: 1024 total in 1 blocks; 256 free (0
chunks); 768 used
pg_namespace_oid_index: 1024 total in 1 blocks; 392 free (0 chunks); 632
used
pg_namespace_nspname_index: 1024 total in 1 blocks; 392 free (0 chunks);
632 used
pg_language_oid_index: 1024 total in 1 blocks; 392 free (0 chunks); 632 used
pg_language_name_index: 1024 total in 1 blocks; 392 free (0 chunks); 632
used
pg_inherits_relid_seqno_index: 1024 total in 1 blocks; 328 free (0
chunks); 696 used
pg_index_indexrelid_index: 1024 total in 1 blocks; 392 free (0 chunks);
632 used
pg_authid_oid_index: 1024 total in 1 blocks; 392 free (0 chunks); 632 used
pg_authid_rolname_index: 1024 total in 1 blocks; 392 free (0 chunks);
632 used
pg_database_datname_index: 1024 total in 1 blocks; 392 free (0 chunks);
632 used
pg_conversion_oid_index: 1024 total in 1 blocks; 392 free (0 chunks);
632 used
pg_conversion_name_nsp_index: 1024 total in 1 blocks; 328 free (0
chunks); 696 used
pg_conversion_default_index: 1024 total in 1 blocks; 192 free (0
chunks); 832 used
pg_class_relname_nsp_index: 1024 total in 1 blocks; 328 free (0 chunks);
696 used
pg_class_oid_index: 1024 total in 1 blocks; 392 free (0 chunks); 632 used
pg_cast_source_target_index: 1024 total in 1 blocks; 328 free (0
chunks); 696 used
pg_attribute_relid_attnum_index: 1024 total in 1 blocks; 328 free (0
chunks); 696 used
pg_attribute_relid_attnam_index: 1024 total in 1 blocks; 328 free (0
chunks); 696 used
pg_amproc_opc_proc_index: 1024 total in 1 blocks; 256 free (0 chunks);
768 used
pg_amop_opr_opc_index: 1024 total in 1 blocks; 328 free (0 chunks); 696 used
pg_amop_opc_strat_index: 1024 total in 1 blocks; 256 free (0 chunks);
768 used
pg_aggregate_fnoid_index: 1024 total in 1 blocks; 392 free (0 chunks);
632 used
Per-database table: 57344 total in 3 blocks; 17120 free (9 chunks);
40224 used
Databases hash: 8192 total in 1 blocks; 3912 free (0 chunks); 4280 used
MdSmgr: 8192 total in 1 blocks; 8080 free (0 chunks); 112 used
LockTable (locallock hash): 8192 total in 1 blocks; 3912 free (0
chunks); 4280 used
Timezones: 48408 total in 2 blocks; 5968 free (0 chunks); 42440 used
Postmaster: 355016 total in 2 blocks; 5800 free (46 chunks); 349216 used
ErrorContext: 8192 total in 1 blocks; 8176 free (4 chunks); 16 used
2006-03-28 14:15:35 BSTERROR:  out of memory
2006-03-28 14:15:35 BSTDETAIL:  Failed on request of size 268435452.

Out of memory? This machine is dedicated to pg and has 16GB of RAM
installed! My AIX knowledge is next to zero, but I'm hoping this helps:

bash-3.00# svmon -U postgres

===============================================================================
User                                 Inuse      Pin     Pgsp  Virtual
postgres                             18989     5304        0    17286

...............................................................................
SYSTEM segments                      Inuse      Pin     Pgsp  Virtual
                                      6767     5292        0     6767

    Vsid      Esid Type Description              PSize  Inuse   Pin Pgsp
Virtual
       0         0 work kernel                       s   6767  5292
0  6767

...............................................................................
EXCLUSIVE segments                   Inuse      Pin     Pgsp  Virtual
                                      7557       12        0     6074

    Vsid      Esid Type Description              PSize  Inuse   Pin Pgsp
Virtual
  1e28be         3 work shared memory segment        s   4078     0
0  4078
  1213f2         1 pers code,/dev/hd2:2809           s   1482     0
-     -
  1425f4         6 work shared memory segment        s   1389     0
0  1389
   525e5         2 work process private              s    150     2
0   150
   82608         2 work process private              s    131     2
0   131
  1b25bb         2 work process private              s     99     2
0    99
  152895         2 work process private              s     74     2
0    74
  1025f0         f work shared library data          s     45     0
0    45
   227e2         2 work process private              s     33     2
0    33
  1125f1         f work shared library data          s     20     0
0    20
   225e2         2 work process private              s     19     2
0    19
  1725f7         f work shared library data          s     11     0
0    11
  172777         f work shared library data          s     10     0
0    10
   827e8         f work shared library data          s      9     0
0     9
   32603         f work shared library data          s      6     0
0     6
  1b25db         - pers /dev/hd3:24                  s      1     0
-     -
   425c4         4 work shared memory segment        s      0     0
0     0
   925e9         5 work shared memory segment        s      0     0
0     0

...............................................................................
SHARED segments                      Inuse      Pin     Pgsp  Virtual
                                      4665        0        0     4445

    Vsid      Esid Type Description              PSize  Inuse   Pin Pgsp
Virtual
   10021         d work shared library text          s   4445     0
0  4445
   f042f         1 pers code,/dev/hd10opt:4164       s    160     0
-     -
  1500d5         1 pers code,/dev/hd2:5664           s     58     0
-     -
  180058         - pers /dev/hd2:45535               s      2     0
-     -


I've checked that the 'postgres' user does not have any limits set with
smitty, and then logged out + in again, but when I restart the
postmaster, I immediately get the same errors from autovac.

This is doubtless some AIX feature that I simply don't know about,
rather than any interaction as a result of pg itself, but AIX admins
must have come across this before :(

Cheers,
Gavin.