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

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Table Of Contents

Chapter 3 75

Deﬁning a Database

Set Part

detail data set. If no data items have a master name following them, the

detail is not related to any master. In this case, the combined length of all

data items in the data set must equal or exceed two halfwords.

sort item name is the name of a detail data item of type U, K, or X which is a part of the

data set being deﬁned. A sort item deﬁnes a sorted path. Each entry added

to a chain of a sorted path will be linked logically in ascending order of the

sort item values. If sort item is omitted, the path order is chronological;

that is, new entries are linked to the end of chains. For performance

reasons, sorted chains should be kept short. (Refer to "Sort Items" in

chapter 2.)

maximum capacity is the maximum number of entries allowed in a data set (data

capacity). It must be less than or equal to 2

−1 (2,147,483,647) and is

limited by the size of the entry as well as the maximum size of a data set,

jumbo or non-jumbo. This number can differ from the number of entries

speciﬁed in the schema itself because the capacity of each detail is

adjusted to represent an even multiple of the blocking factor. Selecting a

very large maximum capacity minimizes the chances that the set will run

out of space.

For non-jumbo data sets, if the capacity expansion parameter, initial

capacity, is speciﬁed and is less (not zero) than the maximum capacity, the

data set is enabled for dynamic expansion. Note that specifying initial

capacity for a jumbo data set will generate an error.

blocking factor is the number of data set records in one block. If a value is not speciﬁed, it

is calculated by DBSCHEMA.

initial capacity is the initial capacity for the data set, that is, the number of entries for

which space will be allocated and initialized when the data set is created.

This number must be between 1 and 2

−1 inclusive but must be less than

or equal to the maximum capacity. Specifying initial capacity for a jumbo

data set will generate an error. This parameter should be used to closely

approximate the current volume of data. If it is very low, there can be

frequent expansions leading to severe disk fragmentation. Initial capacity

is an optional parameter. If initial capacity is not speciﬁed, or if initial

capacity is either zero or equal to the maximum capacity, then dynamic

capacity expansion is not enabled for the data set, and maximum capacity

is used for the data set ﬁle creation.

increment is either the number of entries or the percentage of the initial capacity by

which the data set will be expanded each time its initialized space is

exhausted. If a percentage is used, the percent sign (%) must follow the

incremental amount. This increment parameter can only be used if the

initial capacity parameter is also speciﬁed. This number must be 1 to

32767 inclusive for percent, or 1 to 2

−1 (2,147,483,647) inclusive for

number of entries. If it is very low, there can be frequent expansions

leading to severe disk fragmentation. If it is very high, DBPUT may take a

long time to complete which could impact other database users.

The number of entries deﬁned, or the entries calculated from the percent,