以下摘自goldengate v11.1.1 reference 第324页：

Using COLMAP
Use COLMAP to explicitly map source columns to target columns that have different names
or to specify default column mapping when source and target names are identical. COLMAP
provides instructions for selecting, translating, and moving column data. Do not use this
option for tables being processed in pass-through mode by a data-pump Extract group.

Generating data definitions
When using COLMAP for source and target tables that are not identical in structure, you
must generate data definitions for the source tables, transfer them to the target, and use
the SOURCEDEFS parameter to identify the definitions file.

For source and target structures to be considered identical, they must contain identical
column names (including case, if applicable) and data types, and the columns must be in
the same order in each table. In addition, both tables must have the same column length
semantics for character columns (bytes versus characters).
If the tables have identical structures, and you are using COLMAP for other functions such
as conversion, a source definitions file is not needed. You can use the ASSUMETARGETDEFS
parameter instead.
For more information, see:
● SOURCEDEFS on page 306
● ASSUMETARGETDEFS on page 117
● “Creating a data-Definitions file” in the Oracle GoldenGate Windows and UNIX
Administrator’s Guide.