Re: detached index vs attached index

>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