Re: Encoded Vector Indexes -- MIDRANGE-L

Thanks on the RPG thing, Bruce.

Actually, there have been rebuild performance issues in the past. I believe they've been addressed. By scuttlebutt, I meant that I'd heard this while at IBM but do not know the details.

There is a V4R4 APAR MA22650 with the following info - no PTF:
Abstract
OSP-DB EVI INDEXES REBUILD TIMES EXTREMELY LONG

Error Description
See Problem Summary.

Problem Summary
The customer does a create index to create an EVI index and it
takes 30 seconds. If they update a large number of records in
the file which includes one of the key fields the index gets
rebuilt by one of the QDBSRVxx jobs and takes 23 hours.

Problem Conclusion
Encoded Vector Indexes were not designed to be used with dynamic
data. The intent was for static data, ie. data warehousing.
Inserts, updates, and deletes, especially when affecting a large
number of records, will destroy the performance gains EVI's
were designed for.

If EVI's are necessary for the application, then the proper
design would be to drop the EVI before the update, and once
the update is complete, create the EVI again.

A lot happened, it appears, around V4R4. But there is a V5R2 PTF SI04635 that is intended to continue to improve EVI perofrmance.

This is way too much scuttle. ;-) At the end of the day, EVIs are a great option for improving SQL performance.

Vern

At 11:03 PM 10/23/2003 -0400, you wrote:

----- Original Message -----
From: "Vern Hamberg" <vhamberg@xxxxxxxxxxxxxxxxxxxxxxxxx>
To: "Midrange Systems Technical Discussion" <midrange-l@xxxxxxxxxxxx>
Sent: Thursday, October 23, 2003 19:46
Subject: Re: Encoded Vector Indexes


> Jerry, EVIs are a different kind of index, as you know. They cannot be
used
> for ordering records, only for record selection. This could be a reason to
> keep the non-EVIs, if they are used to support an ORDER BY. Also, I don't
> know whether and EVI index can be used in RPG, as a logical file can.

No, they can not be used in an RPG program.

> EVIs are cool and performance is supposed to be better in V5R2 - there
were
> some problems earlier. No details, just scuttlebutt.


Yes, pure scuttlebutt, I've used them since they were released, and have had
nothing but success with them.