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Label: The execution plan of SQL actually represents the specific execution steps of the target SQL within the Oracle database, and as a tuning, only know if the execution plan chosen by the optimizer is the best execution plan in the current situation, then we can know the direction of the next step. Execution Plan d

Preface: This series of articles includes: 1, understand the hash, Merge, Nested Loop Association strategy. 2. Find and resolve table/index scans in the execution plan. 3. Introduce and find keys to find and resolve them in the execution plan. For performance optimization, the following issues need to be centrally addressed: 1, create a performance baseline for your environment. 2, monitor the current per

How to read ORACLE Execution Plan First, what is the implementation plan An explain plan is a representation of the "access path" is taken when a query is executed within Oracle. second, how to access data At the physical level Oracle reads blocks of data. The smallest amount of data read is a single Oracle block, the largest are constrained by operating syste

Add UserThe first step you want to do every JMeter test plan is to add a Thread Group element. The thread group tells JMeter the number of users you want to impersonate, how long the user should send the request, and how many requests they should send. continue adding Threadgroup elements first select the test plan, click your right mouse button Add a menu, then choose add a?? threadgroup . You should n

SQL Server maintenance plan for database backup (step by Step)First, PrefaceSQL Server Backup and restore all -in-a-kind, including the use of SSMS operation to restore a variety of backup files graphical guidance,SQL Server Database Minimum outage migration scenario , which uses SQL script (T) to complete a full backup, Differential backup, full restore, differential restore, etc.; with the above foundation, we joined the database backup elements, th

Generally, there are four ways to obtain an execution plan: 1. Execute the explain Plan and query the result output table. 2. query the dynamic performance view, which displays the execution plan cached in the database cache (sometimes the result is not found because the execution plan is no longer in the database cach

1 Overview The essence of SQL is a series of pseudoCode, Express what is done, not how to do it. Like other languages, SQL statements must be compiled before they can be run. Therefore, each SQL statement must be interpreted by the compiler before it can be run (SQL optimization is required ). These steps all require running costs, so there is a thing in the database called the execution plan, the compiler will save the compiled SQL into the executi

After executing an SQL statement for the first time in Oracle, the SQL statement is parsed hard, and the execution plan and parse tree are cached in the shared pool. It is convenient to perform this SQL statement again without having to do hard parsing to facilitate application system extension. However, if the SQL corresponds to a change in the table data volume or other reasons, the Shared pool cache execution P