PARALLELS UPDATE 11 TO 13 SERIAL
Serial operations require the schema object to have at least one extent. This allocation of extents is the same for rebuilding indexes in parallel and for moving, splitting, or rebuilding partitions in parallel. Thus, if you create an index with a DOP of 4, the index has at least four extents initially. When you create indexes and tables in parallel, each parallel execution server allocates a new extent and fills the extent with the table or index data. Parallel DDL cannot occur on nonpartitioned tables with LOB columns. Parallel DDL cannot occur on tables with object columns. AS SELECT statements on partitioned tables and parallel CREATE INDEX statements on partitioned indexes execute with a DOP equal to the number of partitions. This statement can be executed in parallel only if the (global) index partition being split is usable.Īll of these DDL operations can be performed in no-logging mode for either parallel or serial execution.ĬREATE TABLE for an index-organized table can be parallelized either with or without an AS SELECT clause.ĭifferent parallelism is used for different operations (see Table 8-2). The parallel DDL statements for partitioned tables and indexes are:ĪLTER TABLE. The parallel DDL statements for nonpartitioned tables and indexes are: Table 8-2 summarizes the operations that can be parallelized in DDL statements. You can parallelize DDL statements for tables and indexes that are nonpartitioned or partitioned. In all cases where the query cannot execute in parallel because of any of these restrictions, the whole query executes serially without giving an error message.
Parallel DML and parallel DDL are not supported with object types, and such statements are always performed serially. Without a MAP function, the query is automatically executed serially. The following restrictions apply to using parallel query for object types.Ī MAP function is needed to parallelize queries involving joins and sorts (through ORDER BY, GROUP BY, or set operations).
There are no limitations on the size of the object types for parallel queries. Parallel query for object types supports all of the features that are available for sequential queries on object types, including:Ĭonstructors to create object type instances Parallel queries can be performed on object type tables and tables containing object type columns. For information about the conditions for parallelizing a query and the factors that determine the DOP, refer to "Rules for Parallelizing Queries". For examples of queries that reference a remote object, refer to "Distributed Transaction Restrictions". For an explanation of how the processes perform parallel queries, refer to "Parallelizing SQL Statements". If the parallel DDL statement includes a subquery, the subquery's DOP is equivalent to the DDL operation.įor information about the query operations that Oracle Database can parallelize, refer to "Operations That Can Be Parallelized". If the parallel DML statement includes a subquery, the subquery's DOP is equivalent to the DML operation.įor parallel DDL, the reference object that determines the DOP is the table, index, or partition being created, rebuilt, split, or moved. Parallel DML also adds some limits to the DOP to prevent deadlock.
The basic rule is to pick the table or index with the largest DOP.įor parallel DML ( INSERT, UPDATE, MERGE, and DELETE), the reference object that determines the DOP is the table being modified by and insert, update, or delete operation. Parallel query looks at each table and index, in the portion of the query being parallelized, to determine which is the reference table. To determine the DOP, Oracle Database looks at the reference objects: These components are determined differently for queries, DDL operations, and DML operations. Parallelization has two components: the decision to parallelize and the degree of parallelism (DOP). You can also query external tables in parallel. You can also parallelize the query portions of DDL statements and DML statements ( INSERT, UPDATE, and DELETE). You can use parallel queries and parallel subqueries in SELECT statements.
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