Execution plan puzzle

I recently come accross a query that used to run fine on production server but suddenly
Execution plans can be affected by different statistics, parallelism due to number of processors, the amount of available RAM in the server, different service packs, different server configuration settings, and the current load on the server. I imagine one or more of these are causing what you are seeing.

SQL server system table corruption

Recently I came across a sage database that has been corrupted. When running DBCC CHECKDB command I was getting the following errors:

There are 226 rows in 1 pages for object "sys.sysprivs".

DBCC results for 'sys.sysschobjs'.

Msg 2511, Level 16, State 1, Line 1

Table error: Object ID 34, index ID 2, partition ID 562949955649536, alloc unit ID 562949955649536 (type In-row data). Keys out of order on page (1:47), slots 66 and 67.

Msg 2511, Level 16, State 1, Line 1

Table error: Object ID 34, index ID 2, partition ID 562949955649536, alloc unit ID 562949955649536 (type In-row data). Keys out of order on page (1:47), slots 72 and 73.

Msg 2511, Level 16, State 1, Line 1

Table error: Object ID 34, index ID 2, partition ID 562949955649536, alloc unit ID 562949955649536 (type In-row data). Keys out of order on page (1:47), slots 93 and 94.

There are 4147 rows in 93 pages for object "sys.sysschobjs".

CHECKDB found 0 allocation errors and 3 consistency errors in table 'sys.sysschobjs' (object ID 34).

Normally the re-indexing should have fixed this type of issue when the base table is user table but it didn't. To fix the issue I have to perform the following commands

use DatabaseName

 go

ALTER DATABASE DatabaseName  SET SINGLE_USER

go

DBCC CHECKDB('DatabaseName', REPAIR_REBUILD)

 go

The outcome from the above command was

Repair: The Nonclustered index successfully rebuilt for the object "sys.sysschobjs, nc1" in database "FCE_Sage".

Msg 8945, Level 16, State 1, Line 1

Table error: Object ID 34, index ID 2 will be rebuilt.

        The error has been repaired.

Msg 2511, Level 16, State 1, Line 1

Table error: Object ID 34, index ID 2, partition ID 562949955649536, alloc unit ID 562949955649536 (type In-row data). Keys out of order on page (1:47), slots 66 and 67.

        The error has been repaired.

Msg 2511, Level 16, State 1, Line 1

Table error: Object ID 34, index ID 2, partition ID 562949955649536, alloc unit ID 562949955649536 (type In-row data). Keys out of order on page (1:47), slots 72 and 73.

        The error has been repaired.

Msg 2511, Level 16, State 1, Line 1

Table error: Object ID 34, index ID 2, partition ID 562949955649536, alloc unit ID 562949955649536 (type In-row data). Keys out of order on page (1:47), slots 93 and 94.

        The error has been repaired..

Latest version of SQL server

To get an idea of what the latest version of SQL server will be, you can ask a SQL guru @Ask SQL Guru

Cannot shrink tempdb

How to shrink tempDB

SELECT * FROM sys.dm_exec_requests WHERE database_id = 2

select * from sys.dm_tran_locks
where resource_database_id= 2

select * from sys.dm_db_session_space_usage
where user_objects_alloc_page_count<> 0

SELECT * FROM sys.all_objects
where is_ms_shipped = 0

DBCC FREEPROCCACHE
BCC SHRINKFILE ('tempdev', 1024)

Purge all data in database

Recently I have been tasked to purge all data in the database. When trying to delete data from tables which have foreign key relationship the standard purge routine will fail or you have to spend time to get which table to purge first. Also there is an issue of identity as when you delete data from the table the identity will not go back to starting point. After few research, I have got the best method which is shown below. 1. Disable all constraints in the database using the following command exec sp_msforeachtable "ALTER TABLE ? nocheck contraint all" 2. Delete all data in the database exec sp_MSForEachTable "DELETE FROM ?" 3. Enable all constraints exec sp_msforeachtable "ALTER TABLE ? WITH CHECK CHECK CONSTRAINT all" 4. Reset tables with identity. Note when you run the following it will give you error if the table doesn't have identity column. Ignore the errors. exec sp_MSforeachtable "DBCC CHECKIDENT ( '?', RESEED, 0)"

SQL server 2012 lauch date

New version of SQL server 2012 launch date is set for 7th of March. The offering will be in three main edition. Details of edition feature comparison can be found at Feature comparison

Enterprise Edition (EE) will be licensed based on compute capacity measured in cores

Business Intelligence (BI) Edition will be available in the Server + CAL model, based on users or devices

Standard Edition (SE) offers both licensing models to address basic database workloads

There will be Web Developer and Express versions but this is not detailed enough and we just have to wait and see.

SQL Server 2012 will continue to offer two licensing options one is based on
one based on computing power and the other is based on based on users or devices. The way the power is measured is not processor rather core based.

Partitioning an existing table and archiving part I

Recently, I have been tasked to come up with a solution to partition a table with clustered index. Previously, I have setup partition from scratch and was loading data to the new partition from non-partitioned table. When a table that you want partition have got a clustered index the job is much easier. I have followed the following steps to achieve my goal.

You don't need to do step 1 to 4 when the database and table/data exists. This is for demo and completeness purposes. You can directly jump to step 5
1.Create database

CREATE DATABASE MyPartitionDB

2. Create table

CREATE TABLE mytableToPartition(MyId INT IDENTITY(1,1), LastUpdated datetime)

3. Populate sample data

declare @timedate datetime
set @timedate = DATEADD(YEAR, -10, GETDATE())
while @timedate < '20121010'
begin
INSERT INTO mytableToPartition (LastUpdated)
values (@timedate)
set @timedate = DATEADD(MINUTE, 20, @timedate)
end

4. Create Index on existing table

CREATE clustered index CL_MyId on mytableToPartition(MyId)

The idea is to move all the data that is created before 2009 as archive and the others as one year partition. Effectively
< 1 Jan 2009
Jan 1 2009 to 31 Dec 2009
Jan 1 2010 to 31 Dec 2010
>= Jan 1 2011
Which means we will have four partitions.

5. Create Filegroups and add file to each Filegroup. For demo purpose I added only one file per Filegroup. As you can see below I created four Filegroups. One Filegroup for each partition. But, you don't have to create four Filegroups. You can use only one Filegroup for all partition but it is better for maintenance purposes and if you want move one Filegroup to different spindle it make it much easier.

ALTER DATABASE MyPartitionDB ADD FILEGROUP FG1;
ALTER DATABASE MyPartitionDB ADD FILEGROUP FG2;
ALTER DATABASE MyPartitionDB ADD FILEGROUP FG3;
ALTER DATABASE MyPartitionDB ADD FILEGROUP FG4;
-- now add file to each filegroup
ALTER DATABASE MyPartitionDBADD FILE(name='FG1',FILENAME='C:\temp\fg1.ndf') TO FILEGROUP FG1
ALTER DATABASE MyPartitionDB ADD FILE(name='FG2',FILENAME='C:\temp\fg2.ndf') TO FILEGROUP FG2
ALTER DATABASE MyPartitionDB ADD FILE(name='FG3',FILENAME='C:\temp\fg3.ndf') TO FILEGROUP FG3
ALTER DATABASE MyPartitionDB ADD FILE(name='FG4',FILENAME='C:\temp\fg4.ndf') TO FILEGROUP FG4

6. Create partition function and scheme

GO
-- create partition function
CREATE PARTITION FUNCTION MyPartitionFunciton (datetime)
AS RANGE RIGHT FOR VALUES ('20090101', '20100101', '20110101');
GO
-- create partition scheme
CREATE PARTITION SCHEME MypartitionScheme
AS PARTITION MyPartitionFunciton TO (FG1,FG2,FG3,FG4)
GO

7. See current status of our table. Up to now our table is in a default partition. See figure below.






8. Move table to partition based on LastUpdated column of the table.
To perform this, I need to drop the index and recreate it on partition scheme that I have created above.

-- drop existing index
DROP INDEX mytableToPartition.CL_MYID
-- re-create index on the partitionscheme
go
CREATE CLUSTERED INDEX CL_MYID on mytableToPartition(myid) on MypartitionScheme(run_date)

Just by creating my clustered index on partition scheme moved all the data in their respective partition. see result set below.



Let us now see where the our data has gone. The following query will show us the Maximum lastupdated value in particular partition, partition number and total number of rows in each partition. See the output result below.






In part II, I will show how easy it is to move archived data and able to delete without affecting performance of your system.

Why going back to ODBC?

Yes, that is my question. For the last few years Microsoft was pushing for OLE DB connectivity. Now, microsoft is going to phase out support for OLE DB. The main reason that have been given is portability. Well, why moved from ODBC in the first place. It is also mentioned on the article that the last OLE DB supported database is the next release of SQL Server (Denali). Microsoft have given a timeline when everybody should port thier application to ODBC 7 years. I am not sure why this move is a must. If it does work, why break and create hasle for the microsoft community who have adopted OLE DB?

Transfer sql server logins between different versions

A very good kb from Microsoft that helps to transfer login between earlier version of SQL Server (7.0 and 2000) to new version. The script and full implication can be found @ Transfer SQL Server logins