如果cache一直增长,并且伴随着cmemthread等待,那么很有可能导致高cpu使用率,如果使用sql server2005低于sp2补丁,那么第一时间就是打上补丁。嫌少动态sql和adhoc来减少发生问题的概率。 短期修复 使用sysadmin角色,因为sysadmin是sql server 最大的权限,不需要做权限检查。那么也就不会产生cache 定期清理cache:DBCC FREESYS...
针对这四大主题,应该对 Performance Counter 多加留意, 也就是这张表sys.dm_os_performance_counters里面的性能指标要熟悉; 硬件层面如果没有问题,等待时间比较合理,那么出问题的就该是软件了,这里涉及到的软件,主要也就是 SQL Execution Plan。 执行计划是如何产生的,如何被优化的,有哪些执行树,执行符号等等。另外...
LIKE 'a%'使用索引LIKE '%a'不使用索引用LIKE '%a%'查询时,查询耗时和字段值总长度成正比,所以不能用CHAR类型,而用VARCHAR。对于字段的值很长的建全文索引 DB Server和Application Server分离,OLTP和OLAP分离 分布式分区视图可用于实现数据库服务器联合体。联合体是一组分开管理的服务器,但它们相互协作分担系统的...
A data page that is not found in the buffer cache must be retrieved from the server's disk subsystem. When the OS has to retrieve the data page from disk, it's known as a hard page fault.When correlating memory performance, disk performance, and CPU performance, a common denominator ...
SQL Server Statistics and Cost Estimation 统计信息(Statistics)会干扰查询优化器(Query Optimizer)生成最优的执行计划。它存储的是表列或者索引列的数值分布统计,也称为柱状统计Histogram。统计信息的过期或者不充分,都能导致优化器评估成本模型(Cost-Based Estimation)失效。所以我们就要时刻监控统计信息的有效性,采取适...
SQL ServerOptimizing SQL Server Query PerformanceMaciej PileckiAt a Glance:Analyzing execution plans Optimizing queries Identifying queries to tuneWhen optimizing your database server, you need to tune the performance of individual queries. This is as important as—perhaps even more important than—tunin...
The “Balanced Data Distributor” for SSISLen Wyatt, SQL Server Performance Team There is...Date: 05/25/2011Kilimanjaro Ships!SQL Server 2008 R2 launches today! While the name “R2” sounds like an incremental update to SS2008...Date: 04/21/2010...
The “Balanced Data Distributor” for SSISLen Wyatt, SQL Server Performance Team There is...Date: 05/25/2011Kilimanjaro Ships!SQL Server 2008 R2 launches today! While the name “R2” sounds like an incremental update to SS2008...Date: 04/21/2010...
SELECT cntr_value as merge_policy_evaluation FROM sys.dm_os_performance_counters WITH(nolock) WHERE object_name LIKE '%columnstore%' AND counter_name ='Total Merge Policy Evaluations' AND instance_name = '_Total' 请注意,此过程专注于为客户提供价值的必要机制。 产品团队不会查看索引中的数据,也不...
SELECT * FROM Orders WHERE CustomerID LIKE 'D%'; --使用索引 SELECT * FROM Orders WHERE CustomerID LIKE '%D'; --不使用索引 在SQL Server 2005执行完成后按 Ctrl+L,可检阅如下图的「执行计划」。 图1 可看出「查询最佳化程序」有使用到索引做搜寻 ...