数据库中NESTED_TABLE_SET_REFShint有什么用

这篇文章将为大家详细讲解有关数据库中NESTED_TABLE_SET_REFS hint有什么用，小编觉得挺实用的，因此分享给大家做个参考，希望大家阅读完这篇文章后可以有所收获。

创新互联主要从事网页设计、PC网站建设（电脑版网站建设）、wap网站建设（手机版网站建设）、成都响应式网站建设公司、程序开发、网站优化、微网站、微信小程序定制开发等，凭借多年来在互联网的打拼，我们在互联网网站建设行业积累了丰富的网站建设、成都网站设计、网站设计、网络营销经验，集策划、开发、设计、营销、管理等多方位专业化运作于一体。

NESTED_TABLE_SET_REFS hint 是 相当于数据泵的操作 expdp 、impdp的操作
INSERT /*+NESTED_TABLE_SET_REFS+*/ 

一个Oracle未公开的hint提示出现了我的面前，再看这个session对应的后台应用，原来是一个export操作,以前还真没注意过，到metalink上查到了如下的解释：

This hint specifies that nested tables should be retrieved as refs.It is used for exporting, importing and loading. It should never be issued by 
user queries, and in fact is unlikely to make a difference if tried.

This is also consistent with seeing large amounts of queries with this hint, and that those queries are not reused. If this is a problem for you, try to export at another time of day. If the exports are really long-running or the system load is constant, try to find out what you are using exports for and suggest alternatives (eg. backup and recovery purposes, etc). If this is a DSS system, you probably have a smaller shared pool and use import/export heavily. If so, it might be a good idea to use a bigger shared pool when doing this activity.

关于“数据库中NESTED_TABLE_SET_REFS hint有什么用”这篇文章就分享到这里了，希望以上内容可以对大家有一定的帮助，使各位可以学到更多知识，如果觉得文章不错，请把它分享出去让更多的人看到。