Unloading data in spanned record format
If you want to unload data from a table that has large LOB or XML fields, consider unloading the data in spanned record format to improve the performance of read/write operations.
About this task
When you unload data in spanned record format, all LOB and XML data for a table space or table space partition can be written to an individual sequential file. This file can reside on DASD and can span multiple volumes. Having such a single sequential file can improve the performance of read/write operations.
UNLOAD SPANNED YES
ignores large block interface (LBI) if used by any output data sets.
Procedure
To unload data in spanned record format:
Specify the SPANNED YES option. Specify in the field specification
list that all LOB and XML data are to be at the end of the record.
Example: The following UNLOAD
statement specifies that the data from table TB1 is to be unloaded
in spanned record format. Notice that in the field specification list,
the CLOB columns are listed at the end and POSITION is not specified.
UNLOAD TABLESPACE TESTDB1.CLOBBASE SPANNED YES
FROM TABLE TB1
(ID
,C1 INTEGER
,C2 INTEGER
,C3 CHAR(100)
,C4 CHAR(100)
,C5 INTEGER
,C6 CHAR(100)
,C7 CHAR(100)
,C8 CHAR(100)
,CLOB1 CLOB
,CLOB2 CLOB
,CLOB3 CLOB) Results
Example of spanned record format: The following figure shows a
conceptual example of a spanned record that was unloaded.
.----------------.------------------.-------------------------------------.
| C1 | C2 | C3| C4 | C5 | C6 | C7 | C8 | Start of CLOB 1 |
+----------------+------------------+------------.------------------------+
| The rest of CLOB 1 | Start of CLOB 2 |
+------------------------------------------------+------------------------+
| more of CLOB 2 |
+----------------------.--------------------------------------------------+
| the rest of CLOB 2 | CLOB 3 |
+----------------------+--------------------------------------------------+
| The next row........................
+---------------------------------------------What to do next