Introduction:
The user has reported a sudden memory usage spike on their SQL Server instance, resulting in degraded performance. You need to troubleshoot and identify the root cause of the memory hike while ensuring the server stabilizes.
Step 1: Confirm Memory Allocation Settings
Preliminary OS, Database, and Task Manager Check
Before diving into SQL Server-specific analysis, perform preliminary checks at the OS and database level:
- Check Server Resource Usage (CPU, Memory, Disk):
- Task Manager / Resource Monitor: Open Task Manager or Resource Monitor to identify system-level bottlenecks such as high CPU, memory, or disk usage.
- Windows Performance Monitor (PerfMon): Monitor key metrics such as Processor Time, Available Memory, and Disk Queue Length to identify any resource saturation.
- Verify SQL Server Memory Utilization:
- Query to Check SQL Server Memory Usage:
SELECT
total_physical_memory_kb / 1024 AS [TotalPhysicalMemoryMB],
available_physical_memory_kb / 1024 AS [AvailablePhysicalMemoryMB],
system_memory_state_desc AS [MemoryState]
FROM sys.dm_os_sys_memory;
Action: This query provides insight into the server’s total and available physical memory to identify memory pressure.
- Check Database and Instance-Level Metrics:
Query to Gather Instance-Level CPU Information:
SELECT
sqlserver_start_time,
cpu_count,
hyperthread_ratio,
physical_memory_kb / 1024 AS [PhysicalMemoryMB],
sql_memory_model_desc
FROM sys.dm_os_sys_info;
- Verify Max Server Memory Settings:
Query:
EXEC sp_configure ‘show advanced options’, 1;
RECONFIGURE;
EXEC sp_configure ‘max server memory’;
Action: Ensure that the max memory setting is configured appropriately, leaving enough memory for the OS and other processes.
Step 2: Review Memory Usage by SQL Server
Verify Memory Usage
Query:
SELECT
(physical_memory_in_use_kb / 1024) AS SQLServer_Memory_MB,
(locked_page_allocations_kb / 1024) AS Locked_Pages_MB,
(page_fault_count) AS Page_Faults,
(memory_utilization_percentage) AS Memory_Utilization_Percent,
(available_commit_limit_kb / 1024) AS Available_Memory_MB
FROM sys.dm_os_process_memory;•
Action: Check if SQL Server is using excessive memory. Adjust the max server memory setting if needed.
Step 3: Identify Major Memory Consumers
Analyze Memory Consumption by Components
Query:
SELECT
type AS Memory_Clerk_Type,
SUM(pages_kb) / 1024 AS Memory_Usage_MB
FROM sys.dm_os_memory_clerks
GROUP BY type
ORDER BY Memory_Usage_MB DESC;• Action: Focus on memory clerk types consuming the most memory. For example, a high CACHESTORE_SQLCP value indicates significant memory use for cached query plans.
Step 4: Analyze Buffer Pool Usage
Check Buffer Pool Utilization
Query:
SELECT
DB_NAME(database_id) AS DatabaseName,
file_id,
page_id,
page_level,
allocation_unit_id
FROM sys.dm_os_buffer_descriptors
WHERE database_id <> 32767ORDER BY database_id;
Action: Investigate databases or tables consuming excessive buffer pool memory. Optimize queries or implement indexes to reduce usage.
Step 5: Investigate High Memory Usage Queries
Identify Memory-Intensive Queries
Query:
SELECT
r.session_id,
r.status,
r.cpu_time,
r.total_elapsed_time,
r.logical_reads,
r.reads,
r.writes,
t.text AS Query_Text
FROM sys.dm_exec_requests r
CROSS APPLY sys.dm_exec_sql_text(r.sql_handle) t
WHERE r.status = ‘running’
ORDER BY r.logical_reads DESC;•
Action: Optimize queries with high logical reads by checking for missing indexes or inefficient joins.
Step 6: Review Query Execution Plans
Analyze Execution Plans
Query:
SELECT
qp.query_plan,
qt.text AS Query_Text
FROM sys.dm_exec_query_stats qs
CROSS APPLY sys.dm_exec_query_plan(qs.plan_handle) qp
CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) qt
WHERE qt.text LIKE ‘%<suspected query pattern>%’;
Action: Address inefficiencies such as missing indexes, scans instead of seeks, or high estimated row counts.
Step 7: Analyze Allocation Units
Determine Memory Usage by Tables or Indexes
Query:
SELECT
OBJECT_NAME(object_id) AS TableName,
index_id,
allocation_unit_id,
type_desc AS AllocationType
FROM sys.allocation_units AS au
JOIN sys.partitions AS p ON au.container_id = p.hobt_id
WHERE allocation_unit_id IN (<list_of_allocation_unit_ids>);
Action: Optimize tables or indexes causing memory pressure. Consider partitioning or archival if necessary.
Step 8: Recommendations to Resolve
Short-Term Fixes
- Free Up Memory:
- DBCC FREEPROCCACHE;
DBCC DROPCLEANBUFFERS;
Note: Use these cautiously in production.
- Throttle Expensive Queries: Optimize queries contributing to memory pressure.
Long-Term Fixes
- Index Optimization: Rebuild or create new indexes.
- Adjust Memory Settings: Ensure max server memory is configured correctly.
- Query Tuning: Rewrite inefficient queries and avoid table scans.
- Partitioning and Archival: Reduce memory usage by partitioning large tables or archiving unused data.
Step 9: Continuous Monitoring
Set Up Monitoring
Query:
SELECT
counter_name,
cntr_value
FROM sys.dm_os_performance_counters
WHERE counter_name LIKE ‘%Memory%’;
Action: Track memory usage patterns and set alerts for specific thresholds to catch issues early.
Conclusion:
- By following these steps, we can effectively troubleshoot and resolve SQL Server memory usage spikes, ensuring optimal server performance and stability.
