Re: detached index vs attached index

At 08:25 PM 9/10/97 -0400, you wrote: } }Hi! } }Is there any easy way to detach indexes in OnLine 5.x and upwards? The ability to build detached indeces arrived with table partitioning, in 7.x. I do not believe you can in 5.x, since index pages are stored with data pages, and mechanism exists to separate. Jon }At 05:57 PM 9/10/97 EDT, you wrote: }} }}>Greeting... }}> }}>Can anyone comment on detached index vs attached index? Thanks in }}>advance! }}> }}>Andy Chang }} }}At one time, Informix often made an issue about the fact that the indexes }}were attached. By attached, we mean that the index is actually contained }}in the same partition (tablespace) that the data pages are located in. The }}thought was that the disk seek time would be shorter if the index pages }}were located physically as close to the data pages as possible.This was }}true with small memory systems with single user applications. By reading }}the index page, there was a rather good possibility that the data page }}would be close by. }} }}However, with larger memory/multi-user systems, this is no longer as much }}of a concern because there is a rather small probability that the read of }}an index item will be followed by a read of the data item. There is a much }}larger probability that the read of the index item will be followed by a }}read from some other user thread. Instead, we are trying to speed-up }}things like read-ahead. By seperating the index from the data pages, we }}can improve performance on scans because the actual scan does not have to }}"skip over" index pages. Also, by detaching the index, the dba can do }}things like insure that the datapages and the index pages are not on the }}same spindle. This should help in the performance of batch type jobs. }} }}All in all, I think detached indexes are a good feature in today's }}environments. }}Madison Pruet }} }Best regards, }Nigel }+-------------------------------------------------------------+ }|Name : Edmund Nigel Gall Tel: (868) 636 3153 | }|Title : Information Systems Specialist Fax: (868) 679 3770 | }|Company: Process Plant Services Limited | }|Address: Atlantic Avenue, Point Lisas Industrial Estate | }| Point Lisas, Couva, Trinidad & Tobago, W.I. | }+----- mailto:nigelg@ppsl.com ------ http://www.ppsl.com -----+ } } ---------------------------------------------------------------------------- --- Jon C. Vemo "Life is like a dogsled team, if you ain't the jvemo@cyberspace.com lead dog the scenery never changes." ---------------------------------------------------------------------------- ---