What Is the Disk Usage Utility?

When you initially implement Lawson applications with an IBM DB2 database, one of the most challenging tasks is calculating the necessary disk space. The IBM DB2 Disk Usage (ibmdu) utility can help you calculate disk usage by providing an estimate (plus or minus ten percent) of the amount of disk space required for the table and index data in a given product line. Use this utility during initial setup or when migrating from another database.

Define the product line in dbdef and create the dictionary before you run ibmdu. If you make changes to the file or index definitions, rebuild the dictionary before you run the utility. The ibmdu utility may be run against the current, new, or old dictionary files.

The ibmdu utility uses the information found in the Lawson dictionary and both law_dba_table and law_dba_index to estimate the file and index object sizes. The utility calculates the space needed for an initial number of records by gathering information from dbdef or from the INITIAL_EXTENT parameters defined in law_dba_table.

Two modes of operation are available—online and offline. In either mode, you must tell the utility what block size to use. Specify the block size by choosing the -bx option, with x representing the block size variable. For example, ibmdu -ob8 dataarea runs offline with a block size of 8K.