imp数据导入时往往大多数的时间都消耗在了索引建立上，我们可以通过为导入会话设置一系列session级别的参数来加速索引的建立:
begin
dbms_system.set_int_param_in_session(&sid,
&serial,
'db_file_multiblock_read_count',
64);
dbms_system.set_int_param_in_session(&sid,
&serial,
'sort_area_size',
209715200);
dbms_system.set_int_param_in_session(&sid,
&serial,
'_sort_multiblock_read_count',
64);
end;
注意在PGA自动管理模式下(即当workarea_size_policy=AUTO时)，自行指定的sort_area_size参数将无法生效。MOS上Bug 8939043叙述了目前dbms_system包的功能仅能修改session级别的布尔和数值类型参数，而无法修改字符串类型参数的问题;所以目前也还无法动态修改其他会话中的workarea_size_policy参数(虽然这个参数在session/system级别是可以动态修改的)。
Hdr: 8939043 11.1.0.7 RDBMS 11.1.0.7 SQL LANGUAGE PRODID-5 PORTID-267
Abstract: SET A CHARACTER-STRING VALUED PARAMETER IN ANOTHER USERS SESSION
Using DBMS_SYSTEM you can set a Boolean parameter with the
SET_BOOL_PARAM_IN_SESSION procedure. Similarly, you can also set an Integer
parameter with the SET_INT_PARAM_IN_SESSION procedure.
There is no procedure in dbms_system or in other package or any other direct
method to set this parameter.
so, it should be a direct method to simulate something like
alter session set cursor_sharing=’EXACT’;
We have a specific process that is running very slowly since upgrading to
11g. If we set optimizer_features_enabled =11.1.0.7 the process runs well.
We can not set this parameter at the database level though as it causes
online errors in other parts of the system.