SQL Server – How to Increase Allocated Memory

Looking at your RAM availablity for this particular server and you are running several databases ranging from 30GB to 5 GB, you definitely need more RAM on this server.

You have not mentioned that this is a stand alone instance or this server is having more than one instance of sql server running.

Your MAX Memory settings seems OK for a server having 8GB RAM. See these suggested best practice settings from Glenn Berry.

I would highly recommend you to do a baseline of your environment using below PERFMON counters to get a good value of your memory configuration :

• SQL Server:Buffer Manager\Page Life Expectancy
• SQL Server:Buffer Manager\Page reads/sec
• Physical Disk\Disk Reads/sec
• Memory\Available Mbytes
• SQL Server: Memory Manager - Total Server Memory
• SQL Server: Memory Manager - Target Server Memory

Total Server Memory: Amount of memory currently allocated to Buffer Pool and not the total amount of memory to SQL Server

Target Server memory: Ideal Size of the buffer pool corresponding to max memory for the instance.

Note: If Total Server Memory > Target Server memory, then it suggests memory pressure.

Below script will help you find LOW or HIGH Memory notifications from sys.dm_os_ring_buffers - system health session :

SELECT CONVERT (varchar(30), GETDATE(), 121) as [RunTime],
dateadd (ms, (rbf.[timestamp] - tme.ms_ticks), GETDATE()) as [Notification_Time],
cast(record as xml).value('(//Record/ResourceMonitor/Notification)[1]', 'varchar(30)') AS [Notification_type],
cast(record as xml).value('(//Record/MemoryRecord/MemoryUtilization)[1]', 'bigint') AS [MemoryUtilization %],
cast(record as xml).value('(//Record/MemoryNode/@id)[1]', 'bigint') AS [Node Id],
cast(record as xml).value('(//Record/ResourceMonitor/IndicatorsProcess)[1]', 'int') AS [Process_Indicator],
cast(record as xml).value('(//Record/ResourceMonitor/IndicatorsSystem)[1]', 'int') AS [System_Indicator],
cast(record as xml).value('(//Record/MemoryNode/ReservedMemory)[1]', 'bigint') AS [SQL_ReservedMemory_KB],
cast(record as xml).value('(//Record/MemoryNode/CommittedMemory)[1]', 'bigint') AS [SQL_CommittedMemory_KB],
cast(record as xml).value('(//Record/MemoryNode/AWEMemory)[1]', 'bigint') AS [SQL_AWEMemory],
cast(record as xml).value('(//Record/MemoryNode/SinglePagesMemory)[1]', 'bigint') AS [SinglePagesMemory],
cast(record as xml).value('(//Record/MemoryNode/MultiplePagesMemory)[1]', 'bigint') AS [MultiplePagesMemory],
cast(record as xml).value('(//Record/MemoryRecord/TotalPhysicalMemory)[1]', 'bigint') AS [TotalPhysicalMemory_KB],
cast(record as xml).value('(//Record/MemoryRecord/AvailablePhysicalMemory)[1]', 'bigint') AS [AvailablePhysicalMemory_KB],
cast(record as xml).value('(//Record/MemoryRecord/TotalPageFile)[1]', 'bigint') AS [TotalPageFile_KB],
cast(record as xml).value('(//Record/MemoryRecord/AvailablePageFile)[1]', 'bigint') AS [AvailablePageFile_KB],
cast(record as xml).value('(//Record/MemoryRecord/TotalVirtualAddressSpace)[1]', 'bigint') AS [TotalVirtualAddressSpace_KB],
cast(record as xml).value('(//Record/MemoryRecord/AvailableVirtualAddressSpace)[1]', 'bigint') AS [AvailableVirtualAddressSpace_KB],
cast(record as xml).value('(//Record/@id)[1]', 'bigint') AS [Record Id],
cast(record as xml).value('(//Record/@type)[1]', 'varchar(30)') AS [Type],
cast(record as xml).value('(//Record/@time)[1]', 'bigint') AS [Record Time],
tme.ms_ticks as [Current Time]
FROM sys.dm_os_ring_buffers rbf
cross join sys.dm_os_sys_info tme
where rbf.ring_buffer_type = 'RING_BUFFER_RESOURCE_MONITOR' 
--and cast(record as xml).value('(//Record/ResourceMonitor/Notification)[1]', 'varchar(30)') = 'RESOURCE_MEMPHYSICAL_LOW'
ORDER BY rbf.timestamp ASC

Some good references :

• How much memory does my SQL Server actually need? - by Jonathan Kehayias
• Performance Tuning using the Waits and Queue
• Great SQL Server Debates: Lock Pages in Memory

I would suggest you to leave MIN Server memory to DEFAULT.

Min server memory controls the minimum amount of Physical memory that sql server will try to keep committed. When the SQL Server service starts, it does not acquire all the memory configured in Min Server Memory but instead starts with only the minimum required, growing as necessary. Once memory usage has increased beyond the Min Server Memory setting, SQL Server won’t release any memory below that amount.

Bob Dorr explains this settings as :

Min Server Memory

Use the min server memory setting with care. This is a floor to SQL Server. Once committed memory to reach the min server memory setting SQL Server won't release memory below the mark. If you set max server memory to 59GB and min server memory to 56GB, but the server needs to back SQL Server down to 53GB SQL Server won't drop below 56GB. When you combine this setting with locked pages in memory the memory can't be paged. This can lead to unwanted performance behaviors and allocation failures.

Searching the web -- internet has plenty of information for max server memory

This is because, this settings is least tuned (people just set it to default), instead max memory is what is generally tuned as it is the "ceiling" for the buffer pool. A good value for max memory will ensure that windows and other processes runing on the server will have enough physical memory to perform their work without forcing sql server to trim.