为什么oracle在create index或者rebuild index的时候不自动将online选项带上?

显示全部楼层 · 2007-4-10 16:54:19

如题

千问 · 2007-4-10 16:54:19

online的时候,空间至少需要正常的两倍,所以,如果索引小了还好!!
如果太大的索引online的时候,空间是个问题!!!
除了这个原因外,online还有下面的限制:
Restrictions on Online Indexes Online indexes are subject to the following
restrictions:
■ Parallel DML is not supported during online index building. If you specify
ONLINE and then issue parallel DML statements, Oracle Database returns an error.
■ You cannot specify ONLINE for a bitmap join index or a cluster index.
■ For a nonunique secondary index on an index-organized table, the number of
index key columns plus the number of primary key columns that are included in
the logical rowid in the index-organized table cannot exceed 32. The logical rowid
excludes columns that are part of the index key.

千问 · 2007-4-10 16:54:19

最初由 nmgzw 发布
[B]online的时候,空间至少需要正常的两倍,所以,如果索引小了还好!!
如果太大的索引online的时候,空间是个问题!!!
除了这个原因外,online还有下面的限制:
Restrictions on Online Indexes Online indexes are subject to the following
restrictions:
■ Parallel DML is not supported during online index building. If you specify
ONLINE and then issue parallel DML statements, Oracle Database returns an error.
■ You cannot specify ONLINE for a bitmap join index or a cluster index.
■ For a nonunique secondary index on an index-organized table, the number of
index key columns plus the number of primary key columns that are included in
the logical rowid in the index-organized table cannot exceed 32. The logical rowid
excludes columns that are part of the index key. [/B]

千问 · 2007-4-10 16:54:19

并且ONLINE的效率很差！多花一倍以上的时间。