Friday, 17 April 2015

Tracking Page Splits

As a DBA, performance tuning is a regular ongoing task. In my experience it is both a reactive and proactive task. The goal, though, is for your proactive efforts to minimise the time spent on the reactive. This has lead me to focus more on page splitting and index fill factor. Specifically, their interaction. There is a lot of information on the web about the benefits and dangers of fill factor and the performance implications of high rates of page splitting, so I will not go into it too much. I will discuss what I've done to monitor page splits. I then tweak fillfactor on the worst offending tables and indexes.

Thursday, 9 April 2015

Running DBCC CHECKDB on TEMPDB

First, a confession. I've been doing it wrong for a long time. Only recently have I learned that TempDB should be included in regular CHECKDB maintenance. Ok, now that I've got that off my chest, I can continue.

So now I've been diligently setting up this task on all servers. NB: TempDB is not available within Maintenance Plans, so you'll need to write the tsql in a job. I add it as a second step in my dbcc maintenance plan job.

Wednesday, 8 April 2015

Full List of SQL Server 2014 DMVs

I'm not sure how useful this will be to others, but I keep searching for a single, comprehensive list of all the SQL Server DMVs with short descriptions. I am looking to complete a certification and this should prove handy for studying. This is certainly no replacement for the full descriptions and examples on MSDN, but I thought it worth putting together.

Thursday, 12 February 2015

Get table and row size data

It often happens that you need to know how big a table is. There are many reasons for this: finding which tables have the most rows; understanding which tables tend to grow the fastest; find which table is using the most space.

I found a nice query on stackexchange.com that listed the tables, row counts and data sizes in a database:

Sunday, 21 December 2014

Emergency Access to SQL Server

There are times when you need to gain access to SQL Server in an emergency. It doesn't happen very often, but it does happen. Actually, part of the problem is that it happens so rarely! We all get to grips with the various back-door commands required of us DBAs when we're training or taking a certification course. But after six months, even two or more years, it all gets a bit rusty.

Therefore, I decided to put together an emergency cheat-sheet. All of these processes are very well documented around the web. My purpose here is purely to list the necessary steps to get access to your server quickly. So I won't be explaining how things work. I will list different options of getting the various steps done.

Tuesday, 14 October 2014

Automating Sliding Partition Windows - Part 4

Recurring Tasks

In the previous posts of this series I both explained the concept of the sliding window partition as well as the way I have configured my system for an automated sliding window. This post will delve into the automated part of the process, the tasks that recur on a regular, in my case monthly, basis.

I have decided to use an SSIS package to execute the various steps of the sliding window, but it is just as valid to wrap the steps into cursors or loops (obviously, you only need a loop if you have more than one table, partition scheme and/or function in your database). Depending on how much you plan on automating there are some challenges in using SSIS. I will be explaining how I've constructed my SSIS package, but it's outside the scope of this post series to explain how to use SSIS. There are many resources on the web that can help you if needed.

Tuesday, 13 May 2014

Automating Sliding Partition Windows - Part 3

It's been a long while since I've worked on this - and believe me I want to as every month I'm spending too much time manually sliding my various partitions! Which is very prone to mistakes.

In the meantime I found a really good post describing an automated sliding partition window that achieves something a little different. It works on the following premise:

  • 7 day partitions that, at the end of each week, are merged into
  • 5 weekly partitions that are then merged into 
  • 6 monthly partitions that are finally merged into 
  • 1 large archive partition

I'm looking at implementing something like this in my company's OLAP database and combined with SQL Server 2012's columnstore indexes I am hoping to get some great performance improvement!

Here's the post:
http://blogs.msdn.com/b/menzos/archive/2008/06/30/table-partitioning-sliding-window-case.aspx


Tuesday, 4 March 2014

Modify Logshipping Restore Job

In my previous post I shared a stored procedure that dynamically creates and executes a restore log script in order to ease the recovery of logshipping after one or more files have been added to a logshipped database.

As I described in that post I was running into this problem on a monthly basis due to a sliding partition window scenario I maintain on several databases. After I wrote the stored procedure it was a lot easier to fix the problem after new files were added. But I still needed to wait for the logshipping restore job to fail and then intervene and execute the SP manually to recover from the failure. Being busy, not to mention forgetful, there were times when logshipping would be broken for several hours at a time.

Unfortunately, you cannot pro-actively inform the failover server that new files are on their way. But what finally did occur to me was to modify the job that restores the transaction log to include the stored procedure. In short, I added a second step that is run only if the first step fails. It works a treat.

Friday, 10 January 2014

An SP to Fix Logshipping After Adding a New Database File

UPDATE: 22 Jan 2014 - Fixed some bugs, added multi-file support and added a few notes

Every month I need to maintain the various sliding partition windows on several databases. If you've read some of my previous posts you may remember that this involves adding new files for the upcoming partitions. My company's databases are also logshipped as part of the disaster recovery strategy.

What invariably happens every month is I add new files make the necessary partition changes and then wonder why, a little later in the day, I'm receiving alerts for failed transaction log restores. The logshipped database obviously doesn't "know" about the new file and I end up with an error message like this:

Monday, 18 November 2013

Database Snapshot Stored Procedure

We've been trying to tighten up the database release process at work. This involves lots of big and small changes including things like using version control software better, documenting database code as well as putting together some default scripts that run with every release.

It occurred to me that even if you have a good process and set of check lists for the release cycle it is still quite easy to miss out on small but ultimately important steps. Things get hectic, last minute changes are made, etc, etc., and the next thing you know you've forgotten a basic, but important, step like creating a database snapshot or disabling scheduled jobs or revoking user access for the duration of the release. There are probably a dozen other small tasks that can be left out.