A control file can specify multiple lengths for the character-data fields CHAR, DATE, and numeric EXTERNAL. If conflicting lengths are specified, then one of the lengths takes precedence. A warning is also issued when a conflict exists. This section explains which length is used.
If you specify a starting position and ending position for one of these fields, then the length of the field is determined by these specifications. If you specify a length as part of the data type and do not give an ending position, the field has the given length. If starting position, ending position, and length are all specified, and the lengths differ, then the length given as part of the data type specification is used for the length of the field, as follows:
POSITION(1:10) CHAR(15)
In this example, the length of the field is 15.
If a delimited field is specified with a length, or if a length can be calculated from the starting and ending positions, then that length is the maximum length of the field. The specified maximum length is in bytes if byte-length semantics are used for the field, and in characters if character-length semantics are used for the field. If no length is specified or can be calculated from the start and end positions, then the maximum length defaults to 255 bytes. The actual length can vary up to that maximum, based on the presence of the delimiter.
If delimiters and also starting and ending positions are specified for the field, then only the position specification has any effect. Any enclosure or termination delimiters are ignored.
If the expected delimiter is absent, then the end of record terminates the field. If TRAILING NULLCOLS is specified, then remaining fields are null. If either the delimiter or the end of record produces a field that is longer than the maximum, then SQL*Loader rejects the record and returns an error.
The length of a date field depends on the mask, if a mask is specified. The mask provides a format pattern, telling SQL*Loader how to interpret the data in the record. For example, assume the mask is specified as follows:
"Month dd, yyyy"
Then "May 3, 2012" would occupy 11 bytes in the record (with byte-length semantics), while "January 31, 2012" would occupy 16.
If starting and ending positions are specified, however, then the length calculated from the position specification overrides a length derived from the mask. A specified length such as DATE(12) overrides either of those. If the date field is also specified with terminating or enclosing delimiters, then the length specified in the control file is interpreted as a maximum length for the field.
"Datetime and Interval Data Types" for more information about the DATE field