TurboIMAGE/XL Database Management System Reference Manual (30391-90012)

Chapter 3 73
Defining a Database
Set Part
the data set, or is zero, but the initial capacity is greater than zero, then
the increment for each expansion is defaulted to ten percent (10%) of the
initial capacity for the data set. If the initial capacity is equal to the
maximum capacity, or the initial capacity is zero, then this indicates the
data set cannot be expanded and increment is ignored.
Examples
NAME: SUP-MASTER,MANUAL /INDEXED (13/12,18),DISC1;
ENTRY: SUPPLIER(1),
STREET-ADD,
CITY,
STATE,
ZIP;
CAPACITY: 2001,501,20%;
Description
The example also shows the data set SUP-MASTER which will reside on Disc1. Assigning
the device class where a data set will reside can provide greater performance for the
TurboIMAGE/XL database and can aid in better use of system resources. An
understanding of how to spread the data sets over multiple disk devices can be obtained
from your system manager. Your system manager will be able to give you a listing of logical
devices and their corresponding device class names (each logical device can have up to
eight names).
To retrieve information on where each data set resides after specifying device classes in
the schema, you can use the MPE/iX command LISTF,3 (after the database is created).
This command lists the device type, logical device number, and the device class name for
each data set in the database. The DBUTIL >>SHOW command can also be used to display
the devices on which data sets reside.
The data set SUP-MASTER will have a B-Tree index created on the key item, SUPPLIER.
B-Tree DBFINDs can be done using SUPPLIER for SUP-MASTER. Also, B-Tree DBFINDs
will be allowed using all of its corresponding search items in the detail sets. In the above
example, SUPPLIER has only one path. Hence, B-Tree DBFIND can be done using the
related search item and the detail data set. The presence of capacity expansion parameters
indicate that it is enabled for dynamic data set expansion.
The example also shows that the maximum capacity is 2001, the initial capacity is 501,
and the increment is 20%.
Another example is capacity defined as follows:
CAPACITY: 2001,501,25;
The maximum capacity is set at 2001, has an initial capacity of 501, and will be
automatically expanded by 25 when the initialized space is exhausted.
To allow dynamic expansion for a master data set, specify the maximum capacity and the
initial capacity when defining the data set. If dynamic expansion is not needed for the data
set, the maximum capacity is the only required parameter.
Verify that there is enough disk space for a data set to be expanded. Performance may be
impacted by the number of entries incremented when a master data set is dynamically
expanded. The number of disk extents used for the data set file may also impact the