Out of memory error from Java stored procedure

I have a Java stored procedure inside Oracle 11g database. The procedure uses lots of memory, so I’m setting the max memory size in same session:

create or replace function setMaxMemorySize(num number) return number
is language java name
'oracle.aurora.vm.OracleRuntime.setMaxMemorySize(long) returns long';
/

select setMaxMemorySize(4*1024*1024*1024) from dual;

I can confirm that max memory has been set:

create or replace function getMaxMemorySize return number
is language java name 'oracle.aurora.vm.OracleRuntime.getMaxMemorySize()
returns long';
/

select getMaxMemorySize() from dual;
4294967295

However, when I run my Java procedure, I get out of memory error from PostgreSQL JDBC driver that the program is using

Exception in thread "Root Thread" org.postgresql.util.PSQLException: 
Ran out of memory retrieving query results.
...
Caused by: java.lang.OutOfMemoryError

But the same program (with same arguments) runs fine outside database by setting the memory limit as JVM argument.

Why is setMaxMemorySize not working? Is there some other parameter I need to set? Java Pool size is already set to 5 GB.