Sql Server缓冲池、连接池等基本知识详解

-- 查看缓冲池使用情况
DBCC DROPCLEANBUFFERS;  -- 清除缓冲池

SELECT 
    COUNT(*) AS cached_pages_count,
    (COUNT(*) * 8.0) / 1024 AS cached_pages_in_MB
FROM sys.dm_os_buffer_descriptors
WHERE database_id = DB_ID('YourDatabaseName');

-- 查看计划缓存使用情况
SELECT 
    cp.objtype AS [CacheType],
    OBJECT_NAME(st.objectid, st.dbid) AS [ObjectName],
    cp.usecounts AS [ExecutionCount],
    st.text AS [QueryText],
    cp.size_in_bytes / 1024 AS [SizeInKB]
FROM sys.dm_exec_cached_plans AS cp
CROSS APPLY sys.dm_exec_sql_text(cp.plan_handle) AS st
WHERE cp.cacheobjtype = 'Compiled Plan'
ORDER BY cp.usecounts DESC;

-- 清除缓冲池
DBCC DROPCLEANBUFFERS;

-- 清除计划缓存
DBCC FREEPROCCACHE;

-- 清除数据缓存
CHECKPOINT;
DBCC DROPCLEANBUFFERS;

-- 缓冲池命中率
SELECT 
    object_name, 
    counter_name, 
    cntr_value
FROM sys.dm_os_performance_counters
WHERE counter_name IN ('Buffer cache hit ratio', 'Buffer cache hit ratio base');

SELECT 
    DB_NAME(dbid) AS DatabaseName,
    COUNT(dbid) AS NumberOfConnections
FROM sys.sysprocesses
WHERE dbid > 0
GROUP BY dbid;

SELECT 
    spid,
    ecid,
    status,
    loginame,
    hostname,
    db_name(dbid) AS DatabaseName,
    cmd,
    request_id
FROM sys.sysprocesses;

SELECT 
    pool_id,
    min_memory_percent,
    max_memory_percent,
    used_memory_kb,
    target_memory_kb,
    max_memory_kb
FROM sys.dm_resource_governor_resource_pools;

SELECT 
    session_id,
    login_time,
    host_name,
    program_name,
    client_interface_name,
    login_name,
    status,
    cpu_time,
    memory_usage,
    logical_reads,
    writes,
    reads
FROM sys.dm_exec_sessions;

SELECT login_name,
Count(0) user_count
FROM Sys.dm_exec_requests dr WITH(nolock)
RIGHT OUTER JOIN Sys.dm_exec_sessions ds WITH(nolock)
ON dr.session_id = ds.session_id
RIGHT OUTER JOIN Sys.dm_exec_connections dc WITH(nolock)
ON ds.session_id = dc.session_id
WHERE ds.session_id > 50
GROUP BY login_name
ORDER BY user_count DESC

ALTER RESOURCE POOL pool_name
WITH (
    MIN_MEMORY_PERCENT = 0,
    MAX_MEMORY_PERCENT = 100
);

ALTER RESOURCE GOVERNOR RECONFIGURE;

DECLARE @session_id INT;

DECLARE session_cursor CURSOR FOR
SELECT session_id 
FROM sys.dm_exec_sessions
WHERE session_id != @@SPID AND is_user_process = 1;

OPEN session_cursor;

FETCH NEXT FROM session_cursor INTO @session_id;

WHILE @@FETCH_STATUS = 0
BEGIN
    EXEC('KILL ' + @session_id);
    FETCH NEXT FROM session_cursor INTO @session_id;
END

CLOSE session_cursor;
DEALLOCATE session_cursor;

ALTER RESOURCE POOL pool_name
WITH (
    MIN_MEMORY_PERCENT = new_min_memory_percent,
    MAX_MEMORY_PERCENT = new_max_memory_percent
);
ALTER RESOURCE GOVERNOR RECONFIGURE;

ALTER WORKLOAD GROUP group_name
USING pool_name;
ALTER RESOURCE GOVERNOR RECONFIGURE;

SELECT 
    pool_id,
    min_memory_percent,
    max_memory_percent,
    used_memory_kb,
    target_memory_kb,
    max_memory_kb
FROM sys.dm_resource_governor_resource_pools;