###sequnece 介绍 http://www.dba-oracle.com/t_rac_tuning_sequence_order_parameter.htm order by 可能会影响性能,但是对确认时间戳 比较重要 order子句保证序列的下一个值是行中的下一个值,不管接收请求的实例是什么.为了举例说明,假设一个序列定义为cache=20.实例1的缓存中有序列值1到20.实例2的缓存中有序列值21到40.通常,并发会话可能按以下顺序生成序列值:1.2.21.3.22.4.23和24.
DBA_TABLES describes all relational tables in the database. Its columns are the same as those in ALL_TABLES. To gather statistics for this view, use the ANALYZE SQL statement. ALL_TABLES describes the relational tables accessible to the current user.