Wednesday Feb 27, 2013

Transporting a Single Partition of a Table

Untitled Document

A feature of the Oracle database that appeared in 11gR1 but seems to have gone largely unnoticed is the ability to transport single (or multiple) partitions of a table to another database. This is particularly useful when archiving out older data held in older partitions of a table.

In previous releases of the Oracle database, it was only possible to transport entire tables, which meant every partition in that table. Therefore the standard methodology used to transport a single partition was to perform a partition exchange at the source database, making the partition a standalone table, and then to transport this table using the normal Transportable Tablespace method to the target database. The result is a standalone table in the target database. The Oracle 11.2 documentation still states that you cannot use the Transportable Tablespace feature to transport a single partition of a table, however we are going to use a different technique, known as ‘datafile copy’ to do exactly that.

The datafile copy technique is actually part of Data Pump. In a similar way to transporting tablespaces, Data Pump is used to export out the metadata describing the objects to be copied to the new database. The datafiles that contain these objects are then copied to the new database, and Data Pump is used to import the metadata. These objects can now be seen by the new database.

This sounds exactly like transporting a tablespace, but there is a difference. In the datafile copy technique we might only be interested in a subset of what is in the datafiles, not the entire contents. This is achieved by invoking Data Pump export in the table mode, rather than tablespace mode. The datafile then effectively becomes an alternative to a dumpfile containing the exported data.

If the only contents of the tablespace in question are a single partition (or subpartition) of a table, then the final result appears to be identical to that achieved using the partition exchange and transportable tablespace technique traditionally used.

Now look at a worked example:
First create a tablespace TRANS to hold the partition to be transported

SQL> CREATE TABLE "OE"."ORDERS_PART"
( "ORDER_ID" NUMBER(12),
"ORDER_DATE" TIMESTAMP(6) WITH local TIME ZONE CONSTRAINT "ORDER_PART_DATE_NN" NOT NULL ,
"ORDER_MODE" VARCHAR2(8),
"CUSTOMER_ID" NUMBER(6) CONSTRAINT "ORDER_PART_CUST_ID_NN" NOT NULL ,
"ORDER_STATUS" NUMBER(2),
"ORDER_TOTAL" NUMBER(8, 2),
"SALES_REP_ID" NUMBER(6),
"PROMOTION_ID" NUMBER(6))
TABLESPACE "EXAMPLE"
PARTITION BY RANGE ("ORDER_DATE")
(PARTITION "H1_2004" VALUES LESS THAN (TIMESTAMP'2004-07-01 00:00:00 +0:00') TABLESPACE TRANS,
PARTITION "H2_2004" VALUES LESS THAN (TIMESTAMP'2005-01-01 00:00:00 +0:00') TABLESPACE TRANS,
PARTITION "H1_2005" VALUES LESS THAN (TIMESTAMP'2005-07-01 00:00:00 +0:00'),
PARTITION "H2_2005" VALUES LESS THAN (TIMESTAMP'2006-01-01 00:00:00 +0:00'),
PARTITION "H1_2006" VALUES LESS THAN (TIMESTAMP'2006-07-01 00:00:00 +0:00'),
PARTITION "H2_2006" VALUES LESS THAN (MAXVALUE));
Table created

And then populate it:

SQL> insert into oe.orders_part select * from oe.orders;
105 rows created.
SQL> commit;

Look at the segments that are contained inside this tablespace:

SQL> select owner, segment_name,partition_name from dba_segments where tablespace_name='TRANS'

OWNER SEGMENT_NAME PARTITION_NAME -------- --------------------- --------------
OE ORDERS_PART H1_2004 OE ORDERS_PART H2_2004

Just like when transporting tablespaces any tablespaces whose datafiles we want to copy must first be made read only.

SQL> alter tablespace trans read only;
Tablespace altered

Now the Data Pump export can be performed. The ‘table’ option is used to indicate which partitions we want to export, and also the ‘transportable=always’ to indicate that the generated dumpfile is to contain the table/partition metadata only as the datafiles containing segments involved will be copied to the new database.

expdp system/oracle tables=oe.orders_part:H1_2004 transportable=always dumpfile=ordersH1_2004.dmp reuse_dumpfiles=y

Export: Release 11.2.0.2.0 - Production on Thu Feb 21 16:20:31 2013

Copyright (c) 1982, 2009, Oracle and/or its affiliates.  All rights reserved.

Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
Starting "SYSTEM"."SYS_EXPORT_TABLE_01":  system/******** tables=oe.orders_part:H1_2004 transportable=always dumpfile=ordersH1_2004.dmp reuse_dumpf
s=y
Processing object type TABLE_EXPORT/TABLE/PLUGTS_BLK
Processing object type TABLE_EXPORT/TABLE/TABLE
Processing object type TABLE_EXPORT/TABLE/END_PLUGTS_BLK
Master table "SYSTEM"."SYS_EXPORT_TABLE_01" successfully loaded/unloaded
******************************************************************************
Dump file set for SYSTEM.SYS_EXPORT_TABLE_01 is:
  D:\DATAPUMP\ORDERSH1_2004.DMP
******************************************************************************
Datafiles required for transportable tablespace TRANS:
  D:\ORADATA\TRANS.DBF
Job "SYSTEM"."SYS_EXPORT_TABLE_01" successfully completed at 16:20:53

Now the datafile is copied to its new location and the TRANS tablespace is made read-write again.

copy d:\oradata\trans.dbf d:\oradata\trans.cpy
        1 file(s) copied.

(If necessary, RMAN can now be invoked to convert the datafile to different platform format.)

SQL> alter tablespace trans read write;

Tablespace altered.

Now move over to the second database and import the partition’s metadata into the database. Use the option ‘partition_options=departition’ which will import the partition as a standalone table. In this example the schema owner is also being changed.

impdp system/oracle partition_options=departition dumpfile=ordersH1_2004.dmp transport_datafiles='d:/oradata/trans.cpy' remap_schema=OE:SH

Import: Release 11.2.0.2.0 - Production on Thu Feb 21 16:21:28 2013

Copyright (c) 1982, 2009, Oracle and/or its affiliates.  All rights reserved.

Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
Master table "SYSTEM"."SYS_IMPORT_TRANSPORTABLE_01" successfully loaded/unloaded
Starting "SYSTEM"."SYS_IMPORT_TRANSPORTABLE_01":  system/******** partition_options=departition dumpfile=ordersH1_2004.dmp transport_datafiles='d:/
data/trans.cpy' remap_schema=OE:SH
Processing object type TABLE_EXPORT/TABLE/PLUGTS_BLK
Processing object type TABLE_EXPORT/TABLE/TABLE
Processing object type TABLE_EXPORT/TABLE/END_PLUGTS_BLK
Job "SYSTEM"."SYS_IMPORT_TRANSPORTABLE_01" successfully completed at 16:21:34

Look for the newly imported table

SQL> select table_name, tablespace_name  from dba_tables
  2  where table_name like 'ORDERS%';

TABLE_NAME			TABLESPACE_NAME
------------------------------ --------------------------------------
ORDERS_PART_H1_2004		TRANS
ORDERS_QUEUETABLE 		EXAMPLE
ORDERS				EXAMPLE
ORDERS				EXAMPLE

Its new name is the name of the original table suffixed with the name of the partition. If this was the only segment that was originally stored in this datafile we would now be finished but, although this partition is the only segment whose metadata was imported into this database, there are actually other segments in this datafile of which this 'new' database does not know anything about.

SQL> select owner, segment_name, partition_name from dba_segments where tablespace_name='TRANS'

OWNER    SEGMENT_NAME         PARTITION_NAME
------------------------------ --------------
SH       ORDERS_PART_H1_2004          

So move the new table to a new tablespace enabling the TRANS tablespace to be dropped.

SQL> alter table sh.orders_part_h1_2004 move tablespace example;

Table altered.

SQL> drop tablespace trans;

Tablespace dropped.

Datafile copying as a means to transport partitions is one of the many features covered in the Oracle Database 11g : Implement Partitioning course.

About the Author:

Gwen Lazenby



Gwen Lazenby is Principal Training Consultant at Oracle. She is part of the UK and IE Core Tech Delivery team, teaching database administration, Spatial and Linux courses. Gwen is also a member of the OU EMEA SME team, with a special responsibility for Oracle Spatial.

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