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The Process
5.2. Improving Load Performance
The performance of XRLOAD can be improved by making changes to the table
description, the storage area, the input file, and the execution of XRLOAD.
For special considerations when loading into partitioned tables, see Appendix D.
5.2.1. Table Description
To make changes to the table description if the input file is in INTERNAL or USER
format:
•
Define primary key columns first.
•
Define primary key columns continuously in primary key order.
•
Define the columns with numeric data types continuously.
•
Wherever null values are not to be stored in a column, use the NOT NULL column
constraint.
5.2.2. Input File
To make changes to the input file:
•
Use INTERNAL format input files to reduce CPU usage.
•
Use shorter patterns in the NULLIF clause to reduce instructions for comparisons on
null checks.
This technique is available only for nonindexed items because of additional
requirements regarding NULLIF clauses for primary key and secondary index
columns as described in 3.3.
•
Allocate the decimal point at a fixed location in each record in the input file if the
input file is in EXTERNAL format and numeric data including the decimal point are
loaded.
•
Sort the records in the table's primary key order and use the SORTED YES clause on
the LOAD command.
•
For INTERNAL and USER format, do not supply null indicators for final columns in a
table defined as NOT NULL.
•
For USER format, if null values are not to be loaded into final columns in a table
defined as NULL ALLOWED in all input records, do not supply null indicators for
those columns.
•
Supply a formal null indictor (a tilde [ ~ ] or N) for those columns into which a null
value may be loaded, even for USER format.
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