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Syntax Specific Nulls

Utilities moving data from a TIBCO Object Service Broker table to an external file or from a file to a TIBCO Object Service Broker table must be able to preserve null values. This section describes the strategies used to store null values in syntax-specific files that are external to TIBCO Object Service Broker.

Syntax Types V, F, and C

Fields containing binary zeroes are considered to be nulls for syntax types F, RD, UN, and V. For syntax C, a field containing all spaces is considered to be null.

Syntax Types B and P Only

By default, if a type B or P field contains the lowest possible value that it can hold, the field is considered to have a null value.

Binary Fields

For binary fields (syntax type B) the following values are considered to be equivalent to nulls:

4-byte B-type field	-2147483648 (X’80000000’)
2-byte B-type field	-32768 (X’8000’)

Packed Decimal Fields

For packed decimal fields, although the lowest possible value is used as the null-equivalent, the alternate negative sign X'B' is used. This means that the lowest possible value can still be used in tables (TIBCO Object Service Broker uses only the standard negative sign X'D').

In a file where the default null-equivalent is to be used in the load process, the following values must not be used in a packed field except to deliberately indicate nulls.

8-byte P-type field	X’999999999999999B’
7-byte P-type field	X’9999999999999B’
6-byte P-type field	X’99999999999B’
5-byte P-type field	X’999999999B’
4-byte P-type field	X’9999999B’
3-byte P-type field	X’99999B’
2-byte P-type field	X’999B’
1-byte P-type field	X’9B’

Semantic Type D (Date) Fields

The value X’80000000’ for a four-byte date is not valid, so it never occurs in a date field. It is therefore a safe null-equivalent value.

The value shown for a two-byte date represents 1890-04-14 (YYYY-MM-DD); therefore, this date is not usable if the default null-equivalent is used.

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