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Database VLDB and Partitioning Guide, 12c Release 1 (12.1)

Balancing the Workload to Optimize Performance

Balancing the Workload to Optimize PerformanceTo optimize performance, all parallel execution servers should have equal workloads. For SQL statements run in parallel by block range or by parallel execution servers, the workload is dynamically divided among the parallel execution servers. This minimizes workload skewing, which occurs when some parallel execution servers perform significantly more work than the other processes. For the relatively

Database VLDB and Partitioning Guide, 12c Release 1 (12.1)

Parameters Establishing Resource Limits for Parallel Operations

Parameters Establishing Resource Limits for Parallel OperationsYou can set initialization parameters to determine resource limits. The parameters that establish resource limits are discussed in the following topics: PARALLEL_FORCE_LOCAL PARALLEL_MAX_SERVERS PARALLEL_MIN_PERCENT PARALLEL_MIN_SERVERS PARALLEL_MIN_TIME_THRESHOLD PARALLEL_SERVERS_TARGET SHARED_POOL_SIZE Additional Memory Requirements for Message Buffers Monitor Memory Usage After Processing Begins

Database VLDB and Partitioning Guide, 12c Release 1 (12.1)

Introduction to Partitioning

Introduction to PartitioningPartitioning addresses key issues in supporting very large tables and indexes by decomposing them into smaller and more manageable pieces called partitions, which are entirely transparent to an application. SQL queries and Data Manipulation Language (DML) statements do not need to be modified to access partitioned tables. However, after partitions are defined, data definition language (DDL) statements

Database VLDB and Partitioning Guide, 12c Release 1 (12.1)

About Parallel DML Operations

About Parallel DML OperationsParallel DML ( PARALLEL INSERT, UPDATE, DELETE, and MERGE ) uses parallel execution mechanisms to speed up or scale up large DML operations against large database tables and indexes. Note: Although DML generally includes queries, in this chapter the term DML refers only to INSERT, UPDATE, MERGE, and DELETE operations. This section discusses the following parallel DML topics: When to Use Parallel DML

Database VLDB and Partitioning Guide, 12c Release 1 (12.1)

Partitioning of XMLIndex for Binary XML Tables

Partitioning of XMLIndex for Binary XML TablesFor binary XML tables, XMLIndex is equipartitioned with the base table for range, hash, and list partitions. For example: CREATE TABLE purchase_order (id NUMBER, doc XMLTYPE) PARTITION BY RANGE (id) (PARTITION p1 VALUES LESS THAN (10), PARTITION p2 VALUES LESS THAN (MAXVALUE)); CREATE INDEX purchase_order_idx ON purchase_order(doc) INDEXTYPE IS XDB.XMLINDEX LOCAL; See Also: Oracle Database Data Cartridge

Database VLDB and Partitioning Guide, 12c Release 1 (12.1)

Performance

Deciding Whether to Partition IndexesDue to the selectivity of queries and high concurrency of OLTP applications, the choice of the right index strategy is indisputably an important decisions for the use of partitioning in an OLTP environment. The following basic rules explain the main benefits and trade-offs for the various possible index structures: A nonpartitioned index, while larger than individual partitioned index segments, always

Database VLDB and Partitioning Guide, 12c Release 1 (12.1)

Splitting a *-Range Subpartition

Splitting a *-Range SubpartitionSplitting a range subpartition of a *-range partitioned table is similar to the description in \" Splitting a Partition of a Range-Partitioned Table \", but the syntax is that of SUBPARTITION rather than PARTITION. For example, the following statement splits a subpartition of the orders table: ALTER TABLE orders SPLIT SUBPARTITION p_pre_may_2007_p_large AT (50000) INTO (SUBPARTITION p_pre_may_2007_med_large

Database VLDB and Partitioning Guide, 12c Release 1 (12.1)

Summary of Partitioned Index Types

Summary of Partitioned Index TypesTable 3-1 summarizes the types of partitioned indexes that Oracle supports. The key points are: If an index is local, then it is equipartitioned with the underlying table. Otherwise, it is global. A prefixed index is partitioned on a left prefix of the index columns. Otherwise, it is nonprefixed. Table 3-1 Types of Partitioned Indexes Type of Index Index Equipartitioned with Table Index Partitioned

Database VLDB and Partitioning Guide, 12c Release 1 (12.1)

Partition Placement

Partition PlacementPartition placement is not a concern if you stripe across all available devices and distribute the load across all available resources. If you cannot stripe data files across all available devices, then consider partition placement to optimize the use of all available hardware resources (physical disk spindles, disk controllers, and channels to disk). I/O-intensive queries or DML operations should

Database VLDB and Partitioning Guide, 12c Release 1 (12.1)

Creating a Local Index Across Multiple Tablespaces

Creating a Local Index Across Multiple TablespacesThe following statement is an example of creating a local index on a table where the index segments are spread across tablespaces ts7, ts8, and ts9. CREATE INDEX employee_ix ON employees_range_hash(department_id) LOCAL STORE IN (ts7, ts8, ts9); This local index is equipartitioned with the base table so that it consists of as many partitions as the base table. Each index partition consists of as many

Database VLDB and Partitioning Guide, 12c Release 1 (12.1)

When to Use Composite Partitioning

When to Use Composite PartitioningComposite partitioning offers the benefits of partitioning on two dimensions. From a performance perspective you can take advantage of partition pruning on one or two dimensions depending on the SQL statement, and you can take advantage of the use of full or partial partition-wise joins on either dimension. You can take advantage of parallel backup and recovery of a single table. Composite partitioning

Database VLDB and Partitioning Guide, 12c Release 1 (12.1)

About Adding Partitions to a Composite *-Range Partitioned Table

Adding a Partition to a *-Range Partitioned TableAdding a new partition to a [range | list | interval]-range partitioned table is as described previously. The database automatically creates interval partitions for an interval-range partitioned table when data is inserted in a specific interval. You can specify a SUBPARTITION clause for naming and providing ranges for specific subpartitions. If no SUBPARTITION clause is specified, then the partition

Database VLDB and Partitioning Guide, 12c Release 1 (12.1)

PARALLEL_MIN_PERCENT

PARALLEL_MIN_PERCENTThis parameter enables users to wait for an acceptable DOP, depending on the application in use. The recommended value for the PARALLEL_MIN_PERCENT parameter is 0 (zero). Setting this parameter to values other than 0 (zero) causes Oracle Database to return an error when the requested DOP cannot be satisfied by the system at a given time. For example, if you set PARALLEL_MIN_PERCENT to 50, which translates

Database VLDB and Partitioning Guide, 12c Release 1 (12.1)

Granules of Parallelism

Block Range GranulesBlock range granules are the basic unit of most parallel operations, even on partitioned tables. Therefore, from Oracle Database perspective, the degree of parallelism is not related to the number of partitions. Block range granules are ranges of physical blocks from a table. Oracle Database computes the number and the size of the granules during run-time to optimize and balance the work distribution

Database VLDB and Partitioning Guide, 12c Release 1 (12.1)

Manageability

ManageabilityIn addition to the performance benefits, partitioning also enables the optimal data management for large objects in an OLTP environment. Every partition maintenance operation in Oracle Database can be extended to atomically include global and local index maintenance, enabling the execution of any partition maintenance operation without affecting the 24x7 availability of an OLTP environment. Partition

Database VLDB and Partitioning Guide, 12c Release 1 (12.1)

Tuning General Parameters for Parallel Execution

Tuning General Parameters for Parallel ExecutionThis section discusses the following topics: Parameters Establishing Resource Limits for Parallel Operations Parameters Affecting Resource Consumption Parameters Related to I/O

Database VLDB and Partitioning Guide, 12c Release 1 (12.1)

Data Integrity Restrictions

Self-Referential IntegrityDML on tables with self-referential integrity constraints is not parallelized if the referenced keys (primary keys) are involved. For DML on all other columns, parallelism is possible.

Database VLDB and Partitioning Guide, 12c Release 1 (12.1)

Enabling and Disabling Heat Map

Enabling and Disabling Heat MapYou can enable and disable heat map tracking at the system or session level with the ALTER SYSTEM or ALTER SESSION statement using the HEAT_MAP clause. For example, the following SQL statement enables Heat Map tracking for the database instance. ALTER SYSTEM SET HEAT_MAP = ON; When Heat Map is enabled, all accesses are tracked by the in-memory activity tracking module. Objects in the SYSTEM and SYSAUX

Database VLDB and Partitioning Guide, 12c Release 1 (12.1)

Splitting Partitions in a *-List Partitioned Table

Splitting Partitions in a *-List Partitioned TablePartitions can be split at both the partition level and at the list subpartition level. Splitting a *-List Partition Splitting a *-List Subpartition

Database VLDB and Partitioning Guide, 12c Release 1 (12.1)

Partitioned Indexes on Composite Partitions

Partitioned Indexes on Composite PartitionsHere are a few points to remember when using partitioned indexes on composite partitions: Subpartitioned indexes are always local and stored with the table subpartition by default. Tablespaces can be specified at either index or index subpartition levels.