SQL Server: Placing Alert for Compatibility Level Change in SQL 2005

Microsoft SQL Server allows its users to keep behavior of a database compatible to its older versions. Like, if someone is using “*=” type of left outer joins in some quires/Stored Procedures as she created it for SQL Server 2000. Though such join are not allowed in SQL Server 2005 and subsequent versions but one still can keep database behavior as SQL Server 2000 by keeping its compatibility level to 80.

Recently, a client reported that someone (DBA or Application) is changing his database compatibility, which should remain compatible to SQL Server 2000 (compatibility level 80). He wants to know at what time this change is being made.

SQL Server 2008 and subsequent versions keep record of this compatibility change to its log, but SQL Server 2005 has no such facility. It means, in SQL Server 2005, you never know when someone has changed compatibility level.

In SQL Server 2008 and subsequent versions one can change compatibility level of a database by following simple TSql statement.

ALTER DATABASE AdventureWorks SET COMPATIBILITY_LEVEL = 90;

But in SQL Server 2005, only method to change this compatability level is its system stored procedure i.e. sys.sp_dbcmptlevel. SQL Profiler is the only place where you can trace when this stored proecdure was executed. But what if, we need to place an alert for this change and generate a mail for this change. Or what if, we need to stop users/applications to change a database compatability level.

Only way to achieve this functionality is,  to update system stored procedure  sp_dbcmptlevel.

Lets perform this task, step by step.

Step 1:  Stop SQL Server 2005 services

Step 2:  Login using DAC (Dadicated Administrative Connection). For this right click on SQL Server 2005 service, on Advanced tab, change startup parameters by adding -m; at existing values.

Step 3: Start SQL Server 2005 services

Step 4: Open SQL Server Management Studio and open Database Engine Query

Step 5: Login as valid sysadmin user or ADMIN:InstanceName

Step 6: Change mssqlsystemresource database to read_write mode

Step 7: It’s the time to update our system stored procedure i.e. sp_dbcmptlevel. If you need to keep only comptability level to 80 or 90 then change following lines of stored procedures with same values i.e.80 or 90 or as per your choice.

select  @cmptlvl60 = 60, 
@cmptlvl60 = 65,
@cmptlvl60 = 70,
@cmptlvl60 = 80,
@cmptlvl60 = 90, 

And if you also need to add a mail alert for this change then add following code in error control portion of stored procedure.

DECLARE @bodyText VARCHAR(200)

SET @bodyText='User '
+ CONVERT(VARCHAR,SYSTEM_USER)  
+' trying to change Compatibility Level of Database '                            + CONVERT(VARCHAR,@dbname)
+ ' at '
 + CAST(GETDATE() AS VARCHAR(50)) 
EXEC msdb.dbo.sp_send_dbmail @recipients='essmess@gmail.com;', --Change Email Address Accordingly 
@subject = 'Compatibility Level Change Alter', 
@profile_name = 'DBTeam', --Change DB mail Profile Accordingly 
@body = @bodyText, 
@body_format = 'TEXT' ;

Here is complete updated script of stored procedure. (This script is only applicable to SQL Server 2005, for SQL Server 2008 and subsequent version, its totally different, which you can get by sp_helptext)

	USE mssqlsystemresource
	GO
	alter procedure sys.sp_dbcmptlevel
	@dbname sysname = NULL, -- database name to change
	@new_cmptlevel tinyint = NULL OUTPUT -- the new compatibility level to change to
	as
	set nocount on
	declare @exec_stmt nvarchar(max)
	declare @returncode int
	declare @comptlevel float(8)
	declare @dbid int -- dbid of the database
	declare @dbsid varbinary(85) -- id of the owner of the database
	declare @orig_cmptlevel tinyint -- original compatibility level
	declare @input_cmptlevel tinyint -- compatibility level passed in by user
	,@cmptlvl60 tinyint -- compatibility to SQL Server Version 6.0
	,@cmptlvl65 tinyint -- compatibility to SQL Server Version 6.5
	,@cmptlvl70 tinyint -- compatibility to SQL Server Version 7.0
	,@cmptlvl80 tinyint -- compatibility to SQL Server Version 8.0
	,@cmptlvl90 tinyint -- compatibility to SQL Server Version 9.0
	--Only compatablility level 80 should be allowed to users and applications for whole instance
	select @cmptlvl60 = 80,
	@cmptlvl65 = 80,
	@cmptlvl70 = 80,
	@cmptlvl80 = 80,
	@cmptlvl90 = 80
	-- SP MUST BE CALLED AT ADHOC LEVEL --
	if (@@nestlevel > 1)
	begin
	raiserror(15432,-1,-1,'sys.sp_dbcmptlevel')
	return (1)
	end
	-- If no @dbname given, just list the valid compatibility level values.
	if @dbname is null
	begin
	raiserror (15048, -1, -1, @cmptlvl60, @cmptlvl65, @cmptlvl70, @cmptlvl80, @cmptlvl90)
	return (0)
	end
	-- Verify the database name and get info
	select @dbid = dbid, @dbsid = sid ,@orig_cmptlevel = cmptlevel
	from master.dbo.sysdatabases
	where name = @dbname
	-- If @dbname not found, say so and list the databases.
	if @dbid is null
	begin
	raiserror(15010,-1,-1,@dbname)
	print ' '
	select 'Available databases:' = name
	from master.dbo.sysdatabases
	return (1)
	end
	-- Now save the input compatibility level and initialize the return clevel
	-- to be the current clevel
	select @input_cmptlevel = @new_cmptlevel
	select @new_cmptlevel = @orig_cmptlevel
	-- If no clevel was supplied, display and output current level.
	if @input_cmptlevel is null
	begin
	raiserror(15054, -1, -1, @orig_cmptlevel)
	return(0)
	end
	-- If invalid clevel given, print usage and return error code
	-- 'usage: sp_dbcmptlevel [dbname [, compatibilitylevel]]'
	if @input_cmptlevel not in (@cmptlvl60, @cmptlvl65, @cmptlvl70, @cmptlvl80, @cmptlvl90)
	begin
	-- Send an email alert
	DECLARE @bodyText VARCHAR(200)
	SET @bodyText='User '
	+ CONVERT(VARCHAR,SYSTEM_USER) +' trying to change Compatibility Level of Database '
	+ CONVERT(VARCHAR,@dbname)
	+ ' at '
	+ CAST(GETDATE() AS VARCHAR(50))
	EXEC msdb.dbo.sp_send_dbmail @recipients='essmess@gmail.com;', --Change Email Address Accordingly
	@subject = 'Compatibility Level Change Alter',
	@profile_name = 'DBTeam', --Change DB mail Profile Accordingly
	@body = @bodyText,
	@body_format = 'TEXT' ;
	raiserror(15416, -1, -1)
	print ' '
	raiserror (15048, -1, -1, @cmptlvl60, @cmptlvl65, @cmptlvl70, @cmptlvl80, @cmptlvl90)
	return (1)
	end
	-- We should not allow the user to change the compatibility level if there exists IV or ICC
	if @orig_cmptlevel >= @cmptlvl80 and @input_cmptlevel < @cmptlvl80
	begin
	-- CHECK FOR INDEXED VIEWS OR INDEXED COMPUTED-COLUMNS
	if exists (select * from sysobjects where xtype = 'V' and id in (select id from sysindexes)) or
	exists (select * from sysobjects o join sysindexkeys k on o.id=k.id
	where o.xtype = 'U' and ColumnProperty(k.id, col_name(k.id, k.colid), 'IsComputed') = 1)
	begin
	-- Cannot set compat mode because database has a view or computed column that is indexed.
	-- These indexes require an 8.0-compatible database.
	raiserror(15414, -1, -1)
	return (1)
	end
	end
	-- Only the SA or the dbo of @dbname can execute the update part
	-- of this procedure sys.so check.
	if (not (is_srvrolemember('sysadmin') = 1)) and suser_sid() <> @dbsid
	-- ALSO ALLOW db_owner ONLY IF DB REQUESTED IS CURRENT DB
	and (@dbid <> db_id() or is_member('db_owner') <> 1)
	begin
	raiserror(15418,-1,-1)
	return (1)
	end
	-- We should not allow the user to change the compatibility level for
	-- replicated or distributed databases
	select @comptlevel = (case @input_cmptlevel
	when 60 then 6.0
	when 65 then 6.5
	when 70 then 7.0
	when 80 then 8.0
	when 90 then 9.0
	end)
	EXEC @returncode = master.dbo.sp_MSreplicationcompatlevel @dbname, @comptlevel
	if @returncode <> 0
	begin
	raiserror(15306, -1, -1)
	return (1)
	end
	-- If we're in a transaction, disallow this since it might make recovery impossible.
	set implicit_transactions off
	if @@trancount > 0
	begin
	raiserror(15002,-1,-1,'sys.sp_dbcmptlevel')
	return (1)
	end
	-- Note: database @dbname may not exist anymore
	-- Change compatibility level
	-- If invoke gets error, exception will abort this proc.
	EXEC %%DatabaseEx(Name = @dbname).SetCompatibility(Level = @input_cmptlevel)
	-- Checkpoint the database that was changed.
	select @exec_stmt = 'use ' + quotename(@dbname, '[') + ' checkpoint'
	EXEC(@exec_stmt )
	-- If checkpoint unsuccessful, restore the old compatibility level,
	-- otherwise update output clevel and flush all the SPs of this database from the cache
	if (@@error <> 0)
	begin
	-- If invoke gets error, exception will abort this proc.
	EXEC %%DatabaseEx(Name = @dbname).SetCompatibility(Level = @orig_cmptlevel)
	return (1)
	end
	dbcc flushprocindb(@dbid)
	select @new_cmptlevel = @input_cmptlevel
	return (0) -- sp_dbcmptlevel

view raw sp_dbcmptlevel.sql hosted with ❤ by GitHub

Step 8: Change mssqlsystemresource database to read_only mode

Step 9: Close SSMS session, stop SQL Server services and change its startup parameters back to normal.

Step 10: Start SQL Server Services and you are done.