Usage Models

Three major usage models are envisioned for the HPL, as follows:

• Reorganizing computer configuration
• Altering the schema of a table
• Loading or unloading external data

Reorganizing Computer Configuration

If you are not changing the table schema, use a no-conversion job to unload and load when you need to reorganize the configuration of your computer or change to a different computer. The no-conversion mode is the fastest means of performing an unload or load because rows are unloaded in Informix internal format with no conversion and reloaded in the same fashion.

For information about preparing for a no-conversion unload/load with ipload, see Using the No Conversion Job Option. To set no-conversion mode when you are using the onpload utility at the command line, use the -fn option. For more information, see The onpload Utility.

Altering the Schema of a Table

When you need to alter a table (add, drop, or change the data type of columns), use the Fixed Internal format. In Fixed Internal format, rows are unloaded in Informix internal format on a column-by-column basis. Thus you can drop, add, or modify columns and still minimize conversion overhead. For more information, see Format Type Group.

Loading and Unloading Data

When you load or unload data from an external source, you must assess the type of data and the amount of conversion that is required so that you can choose appropriate configuration parameters.

The following sections show possible configuration parameters for two different types of load jobs. Suppose your hardware has the following configuration:

• Eight CPU symmetric multiprocessors, each about 40 MIPS
• Several (say 16) 300-megabyte disks (for the database)
• Four 1.2-megabyte tape devices (to load to and unload from)
• 512-megabyte memory

You also have this information about your system:

• The database server is running with seven CPU virtual processors.
• The data that you want to load has a row of about 150 bytes with a mix of INT, DATE, DECIMAL, CHAR, and VARCHAR data types. (This is similar to the LINEITEM table in the TPC-D database).

Settings for a No-Conversion Load or Unload

A no-conversion load or unload is not highly CPU intensive because no conversion is involved. In this case, the load or unload is expected to be limited by the speed of the tape devices. No-conversion loads and unloads are always completed in express mode. For more information, see Using the No Conversion Job Option.

The following table lists sample values of configuration parameters for a raw load.

Express-Mode Load with Delimited ASCII

In an express-mode load with delimited ASCII, the load or unload job is limited by the available CPU. The conversion to or from Informix types to ASCII is the most expensive portion of these operations. Hence, the following configuration might be more appropriate.

The following table lists sample values of configuration parameters for an express-mode load with delimited ASCII.