oracle query tuning tips

Preface In the past decade, Oracle has become one of the world's most professional databases. For IT experts, it is to ensure that their company's productivity is improved by leveraging the powerful features of oracle. One of the most effective methods is to use ORACLE optimization. It has a lot of parameters and technologies to improve the performance of your

dbms_workload_repository. Create_snapshot;We can also use the Dbms_workload_repository package to complete the baseline, modification of the default settings and so on.ADDM (Automatic Database Diagnostic Monitor AWR)is a consultant system within Oracle that can automate some of the optimization recommendations for the most databases, give recommendations for SQL optimization, index creation, and statistics collection.ADDM report Generation:Sqlplus>@?

One: note the connection order in the WHERE clause:Oracle uses a bottom-up sequential parsing where clause, according to which the connection between tables must be written before other where conditions, and those that can filter out the maximum number of records must be written at the end of the WHERE clause.Especially "PRIMARY key id=?" "Such a condition.Second: Avoid using ' * ' in the SELECT clause:During the parsing process, Oracle translates ' *

, which can significantly improve performance. Experience shows that the biggest improvement in SQL Server performance is due to logical database design, index design, and query design. Conversely, the biggest performance problems are often caused by deficiencies in these same areas. In fact, the essence of SQL optimization is that the result is correct, with the optimizer can recognize the statement, fully use the index, reduce the number of I/O tab

lookup, which is optional and defaults to 1.Occurrence: The representative wants to find out the first occurrence of the substring from the source character, which is also optional and defaults to 1.The value of the position is a negative number, then the representation is looked up from right to left.Performance comparison of InStr and likeIn fact, from an efficiency point of view, who can use the index, the query speed will be fast.Like can sometim

Reference | reference Manual | skills | performance | Chinese InnoDB Chinese reference Manual---Dog dog (heart sail) Translation 9 Performance tuning tips (performance tuning tips) 1. If Unix top or Windows Task Manager shows the service's CPU occupancy rate less than 70%, (shows that CPU usage percentage with your I s

Oracle Performance tuning is a broader and somewhat more complex topic, and the biggest problem for ordinary DBAs is where to start and what to do. All the information you know may be someone (a user) who reports a problem with the performance degradation of an application or query, and where do you start when faced with such a problem? Oracle's

. Careful use of large temporary tables and other large table connection query and modification, reduce the system table burden, because this operation will be in one statement multiple times the system table of tempdb. d) Rational use of the algorithm: based on the SQL optimization techniques mentioned above and the SQL optimization content in the ASE Tuning manual, a variety of algorithms are used to com

In the past decade,OracleIt has become one of the most professional databases in the world. For IT experts, IT is to ensure that their company's productivity is improved by leveraging the powerful features of Oracle. One of the most effective methods isOracle Optimization. It has a lot of parameters and technologies to improve the performance of your Oracle database. The following describes how to optimize

Tags: tabs Other applications ABS SSE contains increased data process structure understandingThe parameters of the tuning function in the Oracle database system are called initialization parameters, and the database administrator needs to properly adjust these initialization parameters to optimize the Oracle system according to the actual situation.1 introduction

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MySQL is a powerful open-source database. With more and more database-driven applications, people have been pushing MySQL to its limits. Here are 101 tips for adjusting and optimizing MySQL installation. Some of the techniques are specific to the installation environment, but these ideas are generic. I've divided them into several categories to help you master more of the tuning and optimization techniques

is much higher than that of the composite Index query efficiency, while in 11.2.0.3 version Verify that the ad hoc query efficiency of the common composite index is more efficient than the efficiency of the bitmap index) Create TableT (name_id, gender not NULL, location not NULL, Age_range not NULL, data) as Selectrownum, Decode ( Floor(Dbms_random.value (0,2)),0,'M',1,'F') gender, Ceil (Dbms_random.value

of queries, a large amount of memory may be wasted. This is certainly not what our database administrator wants to see. In practical work, we often need to have a balance between the two. Set a reasonable parameter to make the database less likely to have disk sorting and not overload the server memory. To this end, I have a suggestion. The database administrator should increase the value of this parameter every once in a while and use the Statspack tool to monitor the memory sort and disk-sort

Summary of Oracle Performance Tuning recommendationsPrinciple One: Note the connection order in the WHERE clause:Oracle uses a bottom-up sequential parsing where clause, according to which the connection between tables must be written before other where conditions, and those that can filter out the maximum number of records must be written at the end of the WHERE clause.Especially "PRIMARY key id=?" "Such a

the data processing to the SSAS Cube Dimension (also disk files), again generate unequal disk overhead, in addition to distinct to recalculate, the former need to the membership dimension of this large table to do tier to heavy, the latter only need to the membership level this small dictionary table to do the heavy, obviously the calculation is different weight class, These are just the cost of the process, perhaps you are doing in the night, not care these, then the performance of the

add data to the table (delete, update operations, and so on), add the address of the new record to the index, which slows down the new data. Presumably, to be able to read it, it's not exactly right. Knowing the index, we can add the appropriate index above the table to improve the performance of the query statement.You can look at an index as a unique table, SQL query, if the field is indexed field will b

Supplement to Oracle optimization ldquo; index building rdquo; Supplement to Oracle optimization ldquo; index building rdquo; Indexing is a good method for tuning and greatly improving the query speed. However, in addition to creating an index for each field, you can also create an index as follows: 1. Create

/how-to-drastically-improve-your-app-with-an-afternoon-and-instruments) There are some code that can be used to parse the ISO-8601 date string, and simply rewrite it to use it.Well, just use C to make it look good, but do you believe that we have a better plan!If you can control the date format you are working with, try to choose a Unix timestamp. You can easily convert from timestamp to NSDate: -(nsdate*return[NSDate datewithtimeintervalsince1970:timestamp];}This will be faster than using C

. Create_snapshot; We can also use the Dbms_workload_repository package to complete the baseline, the default settings and other operations.ADDM (Automatic Database diagnostic Monitor AWR)Oracle is an internal consulting system, can automatically complete the most database of some optimization recommendations, giveSQLThe optimization, the creation of the index, the collection of statistics and other suggestions.ADDM report Generation:Sqlplus>@?/rdbms/