Data Definition Language (DDL) Reference Manual

Definition Attributes
Data Definition Language (DDL) Reference Manual—529431-004
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SQLNULLABLE
If the DDL clause NULL is specified for a line item, NOT SQLNULLABLE cannot be
specified or implied for that item.
SQLNULLABLE and NOT SQLNULLABLE cannot be specified on a line item whose
data type has been set by a previous definition, nor on a group or subgroup that
contains such a line item.
An SQL-nullable line item is a word-aligned item regardless of its data type. An implicit
filler of one byte is generated, when necessary, preceding the SQL-nullable line item.
The SQLNULLABLE or NOT SQLNULLABLE attribute is inheritable. That is, a line item
that refers to a definition that is SQL-nullable becomes SQL-nullable as well; a line
item that refers to a definition that is not SQL-nullable becomes itself not SQL-nullable.
A SQL-nullable line item can redefine another line item and can itself be redefined. If
an SQL-nullable line item is redefined, the maximum byte size of the redefining line
item is the specified size of the SQL-nullable line item plus 2.
If an EDIT-PIC clause or a literal string is specified on a null line item, the length of the
string must be less than or equal to the specified size of the line item. Do not include
the added numeric field as part of the available space for the string.
If an odd-byte length is specified on an SQL-nullable line item that has an OCCURS
clause specified or implied, the internal total size of the line item is calculated by:
Occurrences specified * (a 2-byte numeric field + the byte length specified + a
1-byte padded filler)
Because an SQL-nullable line item is word-aligned, a filler is padded to align each
repetition of an SQL-nullable line item with odd-byte length. A padded filler is not
required for a repetition of an SQL-nullable line item specified with even-byte length.
The implicit filler emitted by The DDL compiler is generated explicitly in language
outputs, but not for C or Pascal.
The maximum actual internal byte size of an SQL-nullable line item is 32,767 bytes in
definitions; in records, it is:
File Type Record’s Maximum Length
Entry-sequenced 4072 bytes
Key-sequenced 4062 bytes*
Relative 4072 bytes
Unstructured 4096 bytes
*
In H06.28/J06.17 RVUs with specific SPRs and later RVUs,
the supported maximum record length for a key-sequenced
file is 27648 bytes.
For a list of the required H06.28/J06.17 SPRs, see SPR
Requirements for Increased Enscribe Limits for the
H06.28/J06.17 Release.