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SteveStedman

Status of DBCC CheckDB

So you are checking your database with DBCC CheckDB and of course if you are like me you use the WITH NO_INFOMSGS parameter. But it turns out that CheckDB is taking longer to run that you expected, and you want to check and see what table is currently being checked.

Here is a quick SQL Script that I use to find the current table that is being checked by DBCC CheckDB

use [your database];
go

-- use this to find the session id of DBCC CheckDB
SELECT session_id, start_time, command, percent_complete, total_elapsed_time,
       estimated_completion_time, database_id, user_id, last_wait_type
  FROM sys.dm_exec_requests
 CROSS APPLY sys.dm_exec_sql_text(sql_handle)
 WHERE command like '%DBCC%';  

DECLARE @sessionID as integer = 53; -- enter the session ID of DBCC CheckDB Here

SELECT name, schema_id, type_desc
  FROM sys.objects
 WHERE object_id = (SELECT TOP 1 resource_associated_entity_id
                      FROM sys.dm_tran_locks
					 WHERE request_session_id = @sessionID
					   AND resource_type = 'OBJECT'
					   AND resource_associated_entity_id <> 50);



status of dbcc checkdb


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DBCC CheckDB All Databases

If you use the SQL Server maintenance plans to run DBCC Check DB, you are not allowed to include TempDB in your DBCC CheckDB sequence. For a while I was using maintenance plans, and ending up adding a separate job step to run TSQL to just check TempDB.

Rather than using two different steps, the regular maintenance plan, and a special step for Temp DB, I have instead dumped the regular maintenance plan step, and just used the following TSQL code to run DBCC CheckDB against all databases on the SQL Server.

Option 1: DBCC CheckDB All Databases using sp_msforeachdb

I have included Option 2 below since there are some pretty serious flaws in the sp_msforeachdb script as shown in option 1, specifically sp_msforeachdb will occasionally skip databases. It also has trouble with databases created with certain characters.  Anyway if you want it, here is, but I would recommend paging down to Option 2 which is much more reliable. I would like to thank Patrick Flynn who showed me the flaws in sp_msforeachdb.

The stored procedure sp_msforeachdb takes a parameter of query that will get run against all databases on your SQL Server Instance.


EXEC sp_msforeachdb 'DBCC CHECKDB(''?'') WITH NO_INFOMSGS;';

You can set it up as a maintenance plan like this:

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Database Health Monitor Version 2.1 coming soon

In the next week or two, I will be releasing version 2.1 of the Database Health Monitor application. I am just going through the final testing process now to get it ready for general release. There are a number of new features that have been requested since the release of version 2.0 that will be coming out in version 2.1. The most request feature was the addition of support for the F5 key to refresh reports. There have been several new server or instance level reports added, along with a new section to link to the instance level reports.

Database Health Monitor

Database Health Monitor Version 2.1 New Features

Here is a list of the newly requested features that are complete, and will be available in version 2.1 of the Database Health Monitor.

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Silencing Backup Messages with Trace Flag 3226

ErrorLog_flooded

As a DBA you regularly schedule backups you might have regular full backups, incremental backups and hopefully regular backups. Over time you might realize that your error log is not longer filled with errors, but instead a majority of your error log is filled with backup messages. “Backup Database successfully … “,  “Database backed up…”, “Log was backed up”. This makes it a bit difficult to find the actual errors in this flood of backup messages. Your error log is no longer an error log, but it looks more like a backup log.

Trace Flag 3226

Trace flags in SQL Server are switches or parameters that can be used to turn on or off different features. If you use trace flag 3226 this will turn off all successful backup messages being written to the error log. There are a couple of ways to use trace flag 3226, one is to use DBCC TRACEON to turn on trace flag 3226 for the currently running instance. Using this option will turn it on until the next time the database instance is restarted.

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SQL Server Mentoring – Now Available

Yesterday I was asked by a client about consulting questions and for my help without the typical minimum hourly commitment. He pointed out that he has things that he could use help with that don’t require a multi-hour type project. After thinking it over a bit, I decided to add a SQL Server coaching program to my consulting business, I am calling it my SQL Server Mentoring program.

SQL Server Mentoring Process

Here is how it works if you want to utilize my mentoring services.

Step 1:  Set up a mentoring agreement. You can start this with the free 30 minute consultation form to schedule a time to talk to better understand the service, and so that I can better understand your needs and environment.

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SQL Server Database Corruption Repair

Database corruption repair with SQL Server is one of those things that you generally don’t see every day, but as a DBA, you are expected to be able to fix it quickly without any data loss. From the risk analysis matrix, it is one of those low frequency high impact scenarios that results in an extremely risky situation. This is one of those situations which could lead to great success, or massive failure depending on your training and skills.

These low frequency, high impact, high risk scenarios are the times that you need to rely on your training, or the training of someone more experienced in these areas.

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What is a Page Split

Tables, and indexes are organized in SQL Server into 8K chunks called pages. If you have rows that are 100 bytes each, you can fit about 80 of those rows into a given page. If you update one of those rows to have more data that contains a variable length field like VARCHAR, NVARCHAR, and others, that will cause the page to overflow forcing a page split. The page split takes about half of the data and moves it into a new page, leaving about half in the original page. Another action that causes a page split is to insert a row that based on the indexing would go into a page that is nearly full, if the inserted row doesn’t fit a page split occurs.

If there is room, and your update or insert doesn’t require a split, this is pretty quick to do since SQL Server is just updating one page and then writing it to disk, and to the transaction log. But if the updated or inserted row doesn’t fit, SQL Server needs to allocate a new page, move about half the rows, and then write both pages to disk and to the transaction log. Additionally the pages in all the indexes that point to the data pages need to be updated. Let’s say your table had 1 clustered index, 4 nonclustered indexes, at a minimum 7 pages would be updated, 1 for the clustered index structure, 4 for the nonclustered indexes, and 2 in the data pages in the clustered index. In this specific example the page split would cause a minimum of 7 times the I/O as an insert or update that didn’t require a page split.

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