sqlldr怎么减少redo？

天成

OS:AIX6.1
DATABASE:11.1.0.6
alter table TBSAMUNAPPORTION nologging;
然后用sqlldr（append）导入数据
LOAD DATA INFILE "TBSAMUNAPPORTION.txt" APPEND INTO TABLE
这样是不是可以减少redo?
如果使用UNRECOVERABLE,在加上：DIRECT=TRUE PARALLEL=true
这样是不是会更快？使用PARALLEL会不会有问题？

[ 本帖最后由 天成 于 2012-6-24 16:10 编辑 ]

Maclean Liu(刘相兵

ODM FINDING:


Minimizing Use of the Redo Log

One way to speed a direct load dramatically is to minimize use of the redo log. There are three ways to do this. You can disable archiving, you can specify that the load is unrecoverable, or you can set the SQL NOLOGGING parameter for the objects being loaded. This section discusses all methods.



Intersegment Concurrency with Direct Path

Intersegment concurrency can be used for concurrent loading of different objects. You can apply this technique to concurrent direct path loading of different tables, or to concurrent direct path loading of different partitions of the same table.

When you direct path load a single partition, consider the following items:

    Local indexes can be maintained by the load.

    Global indexes cannot be maintained by the load.

    Referential integrity and CHECK constraints must be disabled.

    Triggers must be disabled.

    The input data should be partitioned (otherwise many records will be rejected, which adversely affects performance).

Intrasegment Concurrency with Direct Path

SQL*Loader permits multiple, concurrent sessions to perform a direct path load into the same table, or into the same partition of a partitioned table. Multiple SQL*Loader sessions improve the performance of a direct path load given the available resources on your system.

This method of data loading is enabled by setting both the DIRECT and the PARALLEL parameters to true, and is often referred to as a parallel direct path load.

It is important to realize that parallelism is user managed. Setting the PARALLEL parameter to true only allows multiple concurrent direct path load sessions.

Maclean Liu(刘相兵

如果使用UNRECOVERABLE,在加上：DIRECT=TRUE PARALLEL=true
这样是不是会更快？

是的 ， 但并行的收益未必很大，如果表没有分区的话

使用PARALLEL会不会有问题？

上面引用的文档介绍了 注意事项：

Local indexes can be maintained by the load.

    Global indexes cannot be maintained by the load.

    Referential integrity and CHECK constraints must be disabled.

    Triggers must be disabled.

    The input data should be partitioned (otherwise many records will be rejected, which adversely affects performance).