Database Software

Hi all.
2 databases of 11.2.0.3.0 version.
I have a script which imports schema from source db to target db via dblinks:

h := dbms_datapump.open ('IMPORT', 'SCHEMA', 'DBBRIDGE');
dbms_datapump.set_parameter (h, 'TABLE_EXISTS_ACTION', 'REPLACE');
dbms_datapump.add_file (h, '!dblog.log', 'DATA_PUMP_DIR', null, dbms_datapump.ku$_file_type_log_file);
dbms_datapump.set_parallel(h,10);
dbms_datapump.metadata_filter (h, 'SCHEMA_LIST', chr(39)||'SCHEMANAME'||chr(39));
dbms_datapump.start_job(h);
dbms_datapump.wait_for_job(h, s);

It work fine on small schemas. When copying the schemas with 4 GB size, datapump hangs.
I checked the size of the schema with this sql:

select sum(bytes)/1024/1024 from dba_segments where owner = 'SCHEMANAME';

It checks this size every 1 min and i see that the 300 megabytes copied in 2 minutes but further the size of the schema is increased by 1 MB per minute or no change. After 6 hours of copying it copied only 350 MB
Also i checked v$session_longops view in which this job have IMPORT status and sofar field is 0.
Datapump logs in DATA_PUMP_DIR don't contains any error.

What could be the problem of this behavior?