DBMS_PCLXUTIL package provides intra-partition parallelism for creating partition-wise local indexes.
DBMS_PCLXUTIL circumvents the limitation that, for local index creation, the degree of parallelism is restricted to the number of partitions as only one parallel execution server process for each partition is used.
See Also:There are several rules concerning partitions and indexes. For more information, see Oracle Database Concepts and Oracle Database Administrator's Guide.
This chapter contains the following topics:
Rules and Limits
DBMS_PCLXUTIL uses the
DBMS_JOB package to provide a greater degree of parallelism for creating a local index for a partitioned table. This is achieved by asynchronous inter-partition parallelism using the background processes (with
DBMS_JOB), in combination with intra-partition parallelism using the parallel execution server.
DBMS_PCLXUTIL works with both range and range-hash composite partitioning.
DBMS_PCLXUTIL package can be used during the following DBA tasks:
Local index creation
BUILD_PART_INDEX assumes that the dictionary information for the local index already exists. This can be done by issuing the create index SQL command with the
CREATE INDEX <idx_name> on <tab_name>(...) local(...) unusable;
This causes the dictionary entries to be created without "building" the index itself, the time consuming part of creating an index. Now, invoking the procedure
BUILD_PART_INDEX causes a concurrent build of local indexes with the specified degree of parallelism.
For composite partitions, the procedure automatically builds local indexes for all subpartitions of the composite table.
Local index maintenance
By marking desired partitions usable or unusable, the
BUILD_PART_INDEX procedure also enables selective rebuilding of local indexes. The
force_opt parameter provides a way to override this and build local indexes for all partitions.
ALTER INDEX <idx_name> local(...) unusable;
Rebuild only the desired (sub)partitions (that are marked unusable):
Rebuild all (sub)partitions using
A progress report is produced, and the output appears on screen when the program is ended (because the
DBMS_OUTPUT package writes messages to a buffer first, and flushes the buffer to the screen only upon termination of the program).
DBMS_PCLXUTIL submits a job for each partition. It is the responsibility of the user/dba to control the number of concurrent jobs by setting the
JOB_QUEUE_PROCESSES correctly. There is minimal error checking for correct syntax. Any errors are reported in the job queue process trace files.
Note:For range partitioning, the minimum compatibility mode is 8.0; for range-hash composite partitioning, the minimum compatibility mode is 8i.
DBMS_PCLXUTIL uses the
DBMS_JOB package, you must be aware of the following limitations pertaining to
You must decide appropriate values for the
job_queue_processes initialization parameter. Clearly, if the job processes are not started before calling
BUILD_PART_INDEX(), then the package will not function properly. The background processes are specified by the following
job_queue_processes=n #the number of background processes = n
Failure conditions are reported only in the trace files (a
DBMS_JOB limitation), making it impossible to give interactive feedback to the user. This package prints a failure message, removes unfinished jobs from the queue, and requests the user to take a look at the
j*.trc trace files.
Provides intra-partition parallelism for creating partition-wise local indexes
This procedure provides intra-partition parallelism for creating partition-wise local indexes.
DBMS_PCLXUTIL.BUILD_PART_INDEX ( jobs_per_batch IN NUMBER DEFAULT 1, procs_per_job IN NUMBER DEFAULT 1, tab_name IN VARCHAR2 DEFAULT NULL, idx_name IN VARCHAR2 DEFAULT NULL, force_opt IN BOOLEAN DEFAULT FALSE);
The number of concurrent partition-wise "local index builds".
The number of parallel execution servers to be utilized for each local index build (1 <=
The name of the partitioned table (an exception is raised if the table does not exist or not partitioned).
The name given to the local index (an exception is raised if a local index is not created on the table
Suppose a table
PROJECT is created with two partitions
PROJ002, along with a local index
A call to the procedure
BUILD_PART_INDEX(2,4,'PROJECT','IDX',TRUE) produces the following output:
SQLPLUS> EXECUTE dbms_pclxutil.build_part_index(2,4,'PROJECT','IDX',TRUE); Statement processed. INFO: Job #21 created for partition PROJ002 with 4 slaves INFO: Job #22 created for partition PROJ001 with 4 slaves