TSQL to suggest optimal MaxServerMemory value

A while ago a colleague of mine wrote a TSQL script to help with suggesting a MaxServerMemory value and a little less time ago we worked together to re-write that script for SQL 2012. While I haven't "checked" it against SQL 2014 the principals are the same, and the reason I am blogging it today is because I am always looking for the script or URL to direct people to so this post makes that easier :)

Of cause there is no black and white recommendation for MaxServerMemory as it is workload dependent. However this script can assist with understanding what that workload requirement is within a SQL Server Instance, please ensure you carefully consider all other memory needs of the server such as additional SQL Instances, and services such as AV, Backups, Monitoring, etc.

SET NOCOUNT ON;

DECLARE 
--@pg_size INT, 
@Instancename varchar(50),
--@RecMem int,
@MaxMem int,
@MaxRamServer int,
@sql varchar(max),
@SQLVersion tinyint


SELECT @SQLVersion = @@MicrosoftVersion / 0x01000000  -- Get major version

-- SELECT physical_memory_kb as ServerRAM_KB from sys.dm_os_sys_info
-- SELECT @pg_size = low from master..spt_values where number = 1 and type = 'E'
-- SELECT @Instancename = LEFT([object_name], (CHARINDEX(':',[object_name]))) FROM sys.dm_os_performance_counters WHERE counter_name = 'Buffer cache hit ratio'
PRINT '------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------'
PRINT 'Optimal MaxServermemory Setting for SQL Server instance ' + @@SERVERNAME  + ' (' + CAST(SERVERPROPERTY('productversion') AS VARCHAR) + ' - ' +  SUBSTRING(@@VERSION, CHARINDEX('X',@@VERSION),4)  + ' - ' + CAST(SERVERPROPERTY('edition') AS VARCHAR) + ')'
PRINT '------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------'

IF @SQLVersion = 11
BEGIN
 PRINT '------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------'
 PRINT 'Total Memory on the Server (MB)' 
 EXEC sp_executesql N'set @_MaxRamServer= (select physical_memory_kb/1024 from sys.dm_os_sys_info)', N'@_MaxRamServer int OUTPUT', @_MaxRamServer = @MaxRamServer OUTPUT
 Print @MaxRamServer
 PRINT '------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------'
END
ELSE
IF @SQLVersion in (10,9)
BEGIN
 PRINT '------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------'
 PRINT 'Total Memory on the Server (MB)' 
 EXEC sp_executesql N'set @_MaxRamServer= (select physical_memory_in_bytes/1024/1024 from sys.dm_os_sys_info)', N'@_MaxRamServer int OUTPUT', @_MaxRamServer = @MaxRamServer OUTPUT
 Print @MaxRamServer
 PRINT '------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------'
END
ELSE 
BEGIN
 PRINT 'Script only supports SQL Server 2005 or later.'
 RETURN
END

--SELECT @RecMem=physical_memory_kb/1024 from sys.dm_os_sys_info

SET @MaxMem = CASE 
    WHEN @MaxRamServer < = 1024*2 THEN @MaxRamServer - 512  /*When the RAM is Less than or equal to 2GB*/
    WHEN @MaxRamServer < = 1024*4 THEN @MaxRamServer - 1024 /*When the RAM is Less than or equal to 4GB*/
    WHEN @MaxRamServer < = 1024*16 THEN @MaxRamServer - 1024 - Ceiling((@MaxRamServer-4096) / (4.0*1024))*1024 /*When the RAM is Less than or equal to 16GB*/

 -- My machines memory calculation
 -- RAM= 16GB
 -- Case 3 as above:- 16384 RAM-> MaxMem= 16384-1024-[(16384-4096)/4096] *1024
 -- MaxMem= 12106

    WHEN @MaxRamServer > 1024*16 THEN @MaxRamServer - 4096 - Ceiling((@MaxRamServer-1024*16) / (8.0*1024))*1024 /*When the RAM is Greater than or equal to 16GB*/
     END
 SET @sql='
EXEC sp_configure ''Show Advanced Options'',1;
RECONFIGURE WITH OVERRIDE;
EXEC sp_configure ''max server memory'','+CONVERT(VARCHAR(6), @maxMem)+';
RECONFIGURE WITH OVERRIDE;'

PRINT '------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------'
PRINT 'Optimal MaxServerMemory Setting for this instance of SQL' 
Print (@sql) 
PRINT '------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------'

Ping back to Tara S. Jana's site http://sqlmasters.jimdo.com/scripts-tsql


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