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Oracle execution plan-processing a situation where parallel hint does not take effectOn itpub, we can see that someone is asking the question that parallel hint does not take effect. I encountered the same problem after doing the experiment, as shown below:The reason is that
Excerpt from the VLDB and partitioning guide There are several main types of parallel execution: 1) Parallel query 2) Parallel DDL 3) Parallel DML 4) Parallel execution function 5) Other types of parallelism The following are described separately, mainly including two aspect
Pq_distribute hints are often used to improve the performance of connection operations between partitioned tables in the Data Warehouse. The Pq_distribute hint allows you to determine how table data rows participating in a connection are allocated between production and consumption parallel query service processes. Pq_distribute prompt accepts three parameters: table name, outer allocation, and internal all
The parallel operation characteristic of Oracle database is to forcibly extract the free resources of database server (mainly CPU resources), and to divide and treat some high load data. Parallel operation is a non-deterministic optimization strategy, which needs to be treated carefully when choosing. Currently, there are several main aspects of using
you specify the degree of parallelism manually, you need to set the number of degrees of parallelism on the SQL statement by hint. Automatic configuration of DOP means that Oracle calculates an automatic adaptive parallelism based on the current actual load and the status of the parallel process pool. The following are some of the parameters related to paralleli
the related target table.The format is as follows:/*+ MERGE_SJ */Examples of Use:SELECT *From Dept Dwhere exists (select/*+ merge_sj */1From EMP Ewhere E.deptno=d.deptnoand e.sal>800);MERGE_SJ hint uses the same MERGE_AJ hint.11, NL_SJNL_SJ is a hint for subqueries, meaning that the optimizer performs nested loop semi-joins on the related target table.The format
statements collected are described in three levels of parallel execution:L Object-levelSets the degree of parallelism for tables and indexes, so that SQL operations involving these objects are performed at a set degree of parallelism.For example: ALTER TABLE outpatient expense record parallel 8;Alter index outpatient expense record _IX_ registration time parallel
Tags: Oracle performance optimization To use parallel hint on a non-partitioned index:The following full table scan parallel hint can take effect: Sql>select/*+full (Dept) parallel (DEPTNBSP;2) */deptnofromdept; Exec
push_join_pred*** no_push_join_pred*** noappend* ORDERED predicates*** Noparallel PARALLEL parallel_index* no_parallel_index*** Hint (hint) was introduced from the Oracle7 to compensate for the defect based on the cost optimizer. Hints a
parametersParallel_min_percent 50% indicates that the minimum threshold for SQL parallelism is specified for execution. If this threshold is not reached, oracle Reports A ora-12827 error.Parallel_adaptive_multi_user TRUE indicates that the SQL concurrency is dynamically adjusted based on system resources, and the best execution performance has been achieved.Parallel_instance_group indicates the parallel op
scan, or an index is accessed through a range scan involving multiple partitions. 2. If the execution involves a full table scan, the statement must contain a parallel hint specifying the corresponding table, or the corresponding table must have a parallel Declaration in its definition. 3. If the execution involves an index range scan spanning multiple partition
1. Order During the historical data transfer-out test, through continuous optimization, including SQL adjustment and database adjustment, we can see from AWR that it is basically difficult to improve performance, therefore, we are prepared to try the features of parallel execution. We can analyze the features of this task and use this technology more easily. This article describes common SQL statements used in pa
. Considerations for setting parallelism in Oracle 2. Concepts and common syntax Parallel Execution improves the performance of a specific task by making full use of hardware resources. It distributes an SQL statement to multiple CPUs for execution at the same time, thus reducing the total time consumption. Parallel
Parallel Oracle database operations, especially in the RAC environment, can improve the database performance to a certain extent. Therefore, it is necessary to understand the relevant initialization parameters. Parallel Oracle database operations, especially in the RAC environment, can improve the database performance
Hint is the embodiment of Oracle database flexibility. Because hint has the highest priority, it is possible to hint the optimizer to generate a specified execution plan based on the needs of the user. Oracle has a wide variety of hint
Environment: Oracle 11.2.0.3 Requirements: Production of a table due to improper design, there is no primary key. Now you need to add the primary key, the amount of data is large, want to build in parallel.1. Direct ADD, hint ora-3001: not implemented function; only single-threaded primary key creationSql> ALTER TABLE t add constraint pk_t primary key (object_id)
author:kj0231320 Team:i.s.t.o The following is the discovery of Oracle HINT Fuzz. Select/*+ no_push_pred (* dual-) * * from dual With a few more hint. This syntax error may cause the current connection session to be interrupted Study for a long time did not find any details of the reason, tracking can not go on
example:SELECT/*+use_hash (BSEMPMS,BSDPTMS) */* from Bsempms,bsdptms WHERE Bsempms. Dpt_no=bsdptms. Dpt_no;/*+driving_site (TABLE) */Enforces query execution on tables that are different from the location selected by Oracle.For example:SELECT/*+driving_site (DEPT) */* from Bsempms,[email protected] WHERE Bsempms. Dpt_no=dept. Dpt_no;/*+leading (TABLE) */Takes the specified table as the first table in the join order./*+cache (TABLE) */When a full table scan is performed, the cache
Select/**//*+ Use_hash (emp,dept) * * Emp.ename,dept.dname from Emp,deptwhere Emp.deptno=dept.deptno; (1,) Use_nl (T1,T2): Represents a nested loop connection when associating a table T1, T2.(2,) Use_merge (T1,T2): Indicates that a sort merge join is used when associating tables T1, T2.(3,) Use_hash (T1,T2): Represents a hash connection when associating a table T1, T2.(4,) leading (T): means that when making a table connection, select T as the driver table.(5,) Ordred: Requires the optimizer to
Prior to using EXP, IMP Lead Library command successfully implemented the Oracle database export, import, on this, yesterday again to the server's newly installed Oracle database with EXP, IMP Guide library, has been reported as "EXP-0006: Internal inconsistent error", so the online Baidu, Try other ways to guide the library, found that the use of EXPDP, IMPDP data pump can also complete the export and impo
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