SQL Server

The video of the online chat that I had with Grant Fritchey about statistics in SQL Server and Oracle is now online. It went pretty well – according to the stats 537 people attended, although the peak concurrency I noticed  was only 467 – of which there were still over 400 after an hour and a quarter.

At the start of the event, James Murtagh put up a quick poll to see how many attendees used SQL Server, how many used Oracle, and how many used both. There’s a degree of bias in the results, no doubt due to the self-selecting nature of the event, but I thought the results were interesting:

Updated 22nd Jan
I’ve previously advertised the fact that the latest online discussion that Red Gate has arranged for me to have with Grant Fritchey will be on 23rd Jan and we will be talking about statistics. If you’ve listened in to any of these talks in the past you’ll realise that they are completely unscripted; what you get is a couple of guys in a (virtual) pub comparing and contrasting their favourite database engines and trying to learn a little bit about how the other technology works.

Here’s a question on OTN from a  SQL Server user that should prompt a few interesting ideas. Re-arranged and paraphrased it goes something like this:

In SQL Server I can write the following code:

DECLARE @Counter INT
SELECT @Counter = 0

UPDATE TempDB.dbo.TransactionDetail
SET @Counter = AccountRunningCount = @Counter + 1
FROM TempDB.dbo.TransactionDetail WITH (TABLOCKX)

What I want to do is more like this:

DECLARE @Total INT = 0
UPDATE StringOutput
set @Total = SumOfLength = @Total + ColLength
OPTION (MAXDOP 1)

How do I do something similar in Oracle ?

After the success of the last Oracle/SQL Server discussion, James Murtagh of Redgate has arranged another online discussion – this time about the different ways in which temporary tables are implemented and used. As before I’ll be doing the Oracle bit and Grant Fritchey will be doing the SQL Server bit.

Update: Now that the event is over, you can listen to the recording at this URL.

… which, for those in the know, means something to do with SQL Server. (The closest physical feature in Oracle  is the index-organized table, the closest sounding name for an Oracle feature is the index cluster - which, just to add to the confusion, must have a specific index that is called the cluster index).

Redgate has arranged for an online debate between an Oracle specialist (me) and a SQL Server specialist (Grant Fritchey) to talk about the strengths and weaknesses of the two mechanisms, discuss why Oracle users seem to be biased towards one implementation and SQL Server users towards the other, and then see where the conversation takes us. This will be followed by a Q&A session.

If you are a director, manager or project manager who works with DBAs, you probably have had the nagging suspicion at one time or another that a DBA’s assertions regarding his or her practices lack an empirical or scientific basis, or are simply deflections intended to pass the buck.

Manager: Mr. DBA, the application is really slow. Do you have any idea what’s wrong?

DBA: Oracle is very complex. It could be any of 100 different possible causes. I will begin checking each. Anyhow, what makes you think it is the database?

In our Remote DBA practice, we frequently perform comprehensive system reviews for our customers on their database services. Among the things we always check for are non-default settings for the database software. We want to validate that any non-default setting is set that way for a good reason, and that any setting that is default really should be that way.

In Oracle, this is easy.  The gv$parameter view has a column, ISDEFAULT, that allows a simple SQL query to show which settings are set to non-default values.

It’s not so easy in SQL Server.  There is a view, master.sys.configurations, but it doesn’t have a way to tell if the setting is default or modified or anything.

Amazon’s Simple Storage Service (S3) is a robust, inexpensive and highly-available internet data storage service.  At Blue Gecko, we occasionally help our customers design and implement S3-based backup strategies.

Interesting question on human mistakes was posted on the DBA Managers Forum discussions today.

As human beings, we are sometimes make mistakes. How do you make sure that your employees won’t make mistakes and cause downtime/data loss/etc on your critical production systems?

I don’t think we can avoid this technically, probably working procedures is the solution.
I’d like to hear your thoughts.

I typed my thoughts and as I was finishing, I thought that it makes sense to post it on the blog too so here we go…

The keys to prevent mistakes are low stress levels, clear communications and established processes. Not a complete list but I think these are the top things to reduce the number of mistakes we make managing data infrastructure or for that matter working in any critical environment be it IT administration, aviation engineering or medical surgery field. It’s also a matter of personality fit – depending on your balance between mistakes tolerance and agility required, you will favor hiring one individual or another.

Regardless of how much you try, there are still going to be human errors and you have to account for them in the infrastructure design and processes. The real disasters happen when many things align like several failure combined with few human mistakes. The challenge is to find the right balance between efforts invested in making no mistakes and efforts invested into making your environment errors-proof to the point when risk or human mistake is acceptable to the business.

Those are the general ideas.

Just a few examples of the practical solutions to prevent mistakes when it comes to Oracle DBA:

• test production actions on a test system before applying in production
• have a policy to review every production change by another senior member of a team
• watch over my shoulder policy working on production environments – i.e. second pair of eye all the time
• employee training, database recovery bootcamp
• discipline of performing routing work under non-privileged accounts

Some of the items to limit impact of the mistakes:

• multiples database controlfiles for Oracle database (in case DBA manually does something bad to one of them – I saw this happen)
• standby database with delayed recovery or flashback database (for Oracle)
• no SPOF architecture
• Oracle RAC, MySQL high availability setup (like sharding or replication), SQL*Server cluster — architecture examples that limit impact of human mistakes affecting a single hardware component

Both lists can go on very long. Old article authored by Paul Vallee is very relevant top this topic — The Seven Deadly Habits of a DBA…and how to cure them.

Feel free to post your thoughts and example. How do you approach human mistakes in managing production data infrastructure?