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SQL Server Memory related Query's





1. /**General Info about Memory Status (SQL 2008 onwards) **/

SELECT total_physical_memory_kb, available_physical_memory_kb,
       total_page_file_kb, available_page_file_kb,
       system_memory_state_desc
FROM sys.dm_os_sys_memory;


2. /**General Info about physical \ Virtual memory low and lock pages (SQL 2008 onwards) **/

SELECT
            physical_memory_in_use_kb/1024 as Memory_used_MB,
            locked_page_allocations_kb/1024 as Memory_locked_page_MB,
    page_fault_count,
            memory_utilization_percentage,
    available_commit_limit_kb/1024 as available_commit_limit_MB,
            process_physical_memory_low,
    process_virtual_memory_low
FROM sys.dm_os_process_memory;

-- If Physical memory is low ,process_physical_memory_low will be non zero value
-- If Virtual memory is low ,process_virtual_memory_low  will be non zero value
-- If locked pages is enabled then
-- Page fault count since server started



3. /** Page Life Expectancy (PLE) value for default instance, for named change object name (SQL 2005 onwards) **/

-- MSSQL$<instance >:Buffer Manager\Page Life Expectancy
-- MSSQL$<instance >:Memory Manager\Target Server Memory (KB)

SELECT cntr_value AS [Page Life Expectancy]
FROM sys.dm_os_performance_counters
WHERE OBJECT_NAME = N'SQLServer:Buffer Manager' -- Modify this if you have named instances
AND counter_name = N'Page life expectancy';

-- PLE is a good measurement of memory pressure.
-- Higher PLE is better. Below 300 for 4 GB Ram is generally bad.
-- Watch the trend, not the absolute value.



4. /**Get total buffer usage by database for current instance (SQL 2005 Onward) **/

SELECT DB_NAME(database_id) AS [Database Name],
COUNT(*) * 8/1024.0 AS [Cached Size (MB)]
FROM sys.dm_os_buffer_descriptors
WHERE database_id > 4 -- system databases
AND database_id <> 32767 -- ResourceDB
GROUP BY DB_NAME(database_id)
ORDER BY [Cached Size (MB)] DESC;

-- Helps determine which databases are using the most memory on an instance
-- This might run longer on a busy system, as its resource intensive query



5. /**Memory Clerk Usage instance level**/

--(SQL 2005 Onwards)
SELECT TOP(20) [type], [name], SUM(pages_kb) AS [SPA Mem, Kb]
FROM sys.dm_os_memory_clerks
GROUP BY [type], [name] 
ORDER BY SUM(pages_kb) DESC;

-- Look for high value for CACHESTORE_SQLCP (Ad-hoc query plans)



--Few of explanations are

Cache
Type
Description
SQL Plans
CACHESTORE_SQLCP
These are cached SQL statements or batches that aren't in stored procedures, functions and triggers
Object Plans
CACHESTORE_OBJCP
These are compiled Plans for stored procedures, functions and triggers
Algebrizer Trees
CACHESTORE_PHDR
An Algebrizer tree is the parsed SQL text that resolves the table and column names


6. /**Find single-use, ad-hoc queries that are bloating the plan cache */

SELECT TOP(100) [text], cp.size_in_bytes/1024 as Size_KB
FROM sys.dm_exec_cached_plans AS cp
CROSS APPLY sys.dm_exec_sql_text(plan_handle)
WHERE cp.cacheobjtype = N'Compiled Plan'
AND cp.objtype = N'Adhoc'
AND cp.usecounts = 1
ORDER BY cp.size_in_bytes DESC;

-- Gives you the text and size of single-use ad-hoc queries that waste space in the plan cache
-- Enabling 'optimize for ad hoc workloads' for the instance can help (SQL Server 2008 and 2008 R2 only)
-- Enabling forced parameterization for the database can help, but test first!





7. /**Breaks down buffers used by current database by object (table, index) in the buffer cache**/

-- Database level queries (switch to your database)
-- (SQL 2008 onwards)
SELECT OBJECT_NAME(p.[object_id]) AS [ObjectName],
p.index_id, COUNT(*)/128 AS [Buffer size(MB)],  COUNT(*) AS [BufferCount],
p.data_compression_desc AS [CompressionType]
FROM sys.allocation_units AS a
INNER JOIN sys.dm_os_buffer_descriptors AS b
ON a.allocation_unit_id = b.allocation_unit_id
INNER JOIN sys.partitions AS p
ON a.container_id = p.hobt_id
WHERE b.database_id = CONVERT(int,DB_ID())
AND p.[object_id] > 100
GROUP BY p.[object_id], p.index_id, p.data_compression_desc
ORDER BY [BufferCount] DESC;

-- This might take some time on busy system, Performance intensive query




8. /**Top Cached SPs by Total Logical Reads and Logical reads relate to memory pressure (SQL 2008 onwards) **/

SELECT TOP(25) p.name AS [SP Name], qs.total_logical_reads AS [TotalLogicalReads],
qs.total_logical_reads/qs.execution_count AS [AvgLogicalReads],qs.execution_count,
ISNULL(qs.execution_count/DATEDIFF(Second, qs.cached_time, GETDATE()), 0) AS [Calls/Second],
qs.total_elapsed_time, qs.total_elapsed_time/qs.execution_count
AS [avg_elapsed_time], qs.cached_time
FROM sys.procedures AS p
INNER JOIN sys.dm_exec_procedure_stats AS qs
ON p.[object_id] = qs.[object_id]
WHERE qs.database_id = DB_ID()
ORDER BY qs.total_logical_reads DESC;

-- This helps you find the most expensive cached stored procedures from a memory perspective
-- You should look at this if you see signs of memory pressure





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