Sunday, May 18, 2008

How do you maintain MSDB database?

Last week I visited our client who has pretty big databases and performs BACKUP LOG ..operation on almost all user databases. Now, one of the most critical databases got corrupted and the DBA was pretty confident that he won't loose any data (as he had backup of log file) and brings the database from the backup within 10-12 minutes.

They also have very well written stored procedure that does RESTORE DATABASE based on name of the database and number of log files to be restored. They run the stored procedure and it has been running for almost 5 hours till DBA canceled the process. What happened? Why it has taken so much time? I thought about it and asked him a question,:-"Have you ever cleared backup history?", he replied that he hasn't. Then we checked backupset system database that contained more than one million rows!!!!

I remember SQL Server MVP Geoff N.Hiten wrote the blog about the issue and I even posted a comment on.Please check the following article

It tooks only 3 minutes to run a script that create indexes and about 15 munutes to run
use msdb


declare @OldestDate datetime

set @OldestDate = getdate() -100

exec sp_delete_backuphistory @OldestDate

Now that it is finished , our RESTORE command took only 12 minutes to complete.
I'd like to point out how important is to clear backup history (Fortunately, in SQL Server 2005 we have builtin taks to do the job) as on time 'X' you will succefully restore a needed database.

Monday, May 5, 2008

Getting row count of table in SQL Server 2005

It is much easier in SQL Server 2005 to get row count per table.

[RowCount] = SUM
WHEN (pt.index_id < 2) AND (au.type = 1) THEN pt.rows
sys.tables tbl
INNER JOIN sys.partitions pt
ON tbl.object_id = pt.object_id
INNER JOIN sys.allocation_units au
ON pt.partition_id = au.container_id

Sunday, May 4, 2008

Getting next value

Hi folks. I'd like to share with you some technique to get a next value from the table means to create your own sequence mechanism.
As we all know that an Identity property may have gaps, so use the below script to retrieve a next value. We create a table with a one row and a only one column which holding the last used sequence value.

CREATE TABLE seq(col int not null);
INSERT INTO seq values(0);

CREATE PROC spget_nextseq @next_val AS INT OUTPUT
UPDATE seq SET @next_val= col = col + 1;

-- usage
DECLARE @i as int;
EXEC spget_nextseq @i output;

Note, in OLTP application where many connections run this script you may end up with deadlocks. One way to pevent it is using lock hint called TABLOCK

ALTER PROC spget_nextseq @next_val AS INT OUTPUT
UPDATE seq SET @next_val= col = col + 1 FROM seq WITH (TABLOCK);