ORA-04030: out of process memory when trying to allocate 8224 bytes (sort subheap,sort

Hi, I wonder what part was out of memory.  What can be done ?
Db version 10.2.0.3.
Server sol 10 has 10 gb ----------------->OS Solaris 5.10 , and has 10GB
shared_pool =912 m
db_cache = 800 m
large_pool = 144 m
java_pool = 144
------------------------------------
total sga 2015 m
pga_aggregate_target=1Gb
sga_max_size=6gb
sga_target=6gb
parallel_adaptive_multi_user=TRUE
parallel_automatic_tuning=FALSE
parallel_execution_message_size=2152
parallel_max_servers=16
parallel_server=FALSE
parallel_server_instance=1
parallel_threads_per_cpu=2

Maximum pga allocated = 746 mb

Following is the script:

proddb:/export/home/oracle/dba/scripts> more dbms_stat_siebel2.sql
EXECUTE DBMS_STATS.GATHER_SCHEMA_STATS (OWNNAME=> 'SIEBEL', DEGREE=> 5, CASCADE=