Run this script in stream admin user at target database, to prevent drop for the tables. 
Example
conn STRMADMIN/[email protected]
create or replace procedure
IGNORE_DROP_TABLE (in_any IN SYS.ANYDATA
)
is
lcr SYS.LCR$_DDL_RECORD;
rc PLS_INTEGER;
begin
rc := in_any.GETOBJECT(lcr);
if lcr.GET_COMMAND_TYPE != ‘DROP TABLE’
then
lcr.execute();
end if;
END;
/
begin
dbms_apply_adm.alter_apply(
apply_name => ‘STREAMS_APPLY’,
ddl_handler => ‘IGNORE_DROP_TABLE’);
end;
/
