![]() ![]() In the Add counters dialog select the machine name in the drop-down list.Select Monitoring Tools, Performance Monitor in the left pane.Open Control Panel, select System and Security, Administrative Tools, and click Performance Monitor.Open Start, Run (Windows + R for Windows 8), type perfmon, and press Enter.Open Start (Windows + C for Windows 8), select Search, type perfmon, and press Enter.Start Windows Performance Monitor, using one of the following methods:.If the values are constantly high, further investigation is required. Another recommendation is that the number of Recompilations/sec should be less than 10% of Compilations/sec. However, it is also recommended to have the Compilations/sec value to be less than 10% of the Batch Requests/sec value. You should watch for the metric trend and set a baseline. The ideal value for the number of recompilations per second is zero. A high value is a clear indication of frequent recompilations that lead to processor stress and SQL Server performance degradation. The metric that shows the number of query and procedure recompilations in a second is SQL Re-Compilations/Sec. It’s expected that the value is high on SQL Server start up, but is should fall and stabilize after a while. The metric shows the number of query and procedure compilations in a second. It’s located in the SQL Server Statistics section. The metric that tracks the number of compilations per second is SQL Compilations/Sec. Windows Performance Monitor can be used to track both compilations and recompilations. Detecting recompilations using Windows Performance Monitor In the earlier versions, all statements in the stored procedure were recompiled, which affected SQL Server performance even more. Since SQL Server 2005, only the statement that causes a recompilation is recompiled. ![]() It’s recommended not to save any of SET options (ANSI_NULLS, Quoted_identifier, etc.) in a stored procedure, as they cause recompilation There will be three recompilations, as indicated in the comments The query will be recompiled when it reaches the first data operation. In other words, when DDL (Data Definition Language) statements are interleaved with DML (Data Manipulation Language) statements. When you execute a query or stored procedure where a schema change is followed by a data operation, such as SELECT, INSERT, UPDATE, or DELETE. The threshold can be changed using the KEEP PLAN query hint, as described in Frequent query recompilations – a SQL query performance killer –introduction When a table referenced by the query has more data changes than specified by the threshold. Table and view column changes (a column added or dropped) ![]() When a schema of an object referenced by the query is changed. When a database that contains the stored procedure, or any object referenced by the query is restored. New queries are compiled, added to cache which size is limited, so at a point, the old query execution plans are moved out of cache to make space for the new ones. Whenever SQL Server is restarted, all query execution plans stored in cache are removed from cache.Įxcessive SQL Server activity. ![]()
0 Comments
Leave a Reply. |