By default, pairs of source and target temp-tables being copied by the COPY-DATASET or COPY-TEMP-TABLE method must have compatible definitions. The loose-copy-mode option overrides this default.

For the COPY-DATASET method, if loose-copy-mode is true, the parameter applies to each temp-table buffer in the ProDataSet. Thus, the remainder of this paragraph applies to both the COPY-DATASET and COPY-TEMP-TABLE methods. If loose-copy-mode is true for a temp-table buffer, the AVM effectively performs a BUFFER-COPY from source to target. BUFFER-COPY is more flexible than the default behavior of COPY-TEMP-TABLE or COPY-DATASET because it matches each source field by name to its corresponding field in the target, and ignores fields that do not match, without error. This is somewhat more expensive than the default behavior of COPY-DATASET and COPY-TEMP-TABLE, which assumes compatible definitions field-for-field between source and target. When loose-copy-mode is true, the AVM checks for an existing field-mapping between the two buffers specified in a previous ATTACH-DATA-SOURCE operation. If the source temp-table is in fact the Data-Source for the target, then its field-mapping is used to match up field pairs with differing names, just as for BUFFER-COPY. If there is no ATTACH-DATA-SOURCE between the two buffers, the copy is done by matching field names and only copying those fields that appear in both source and target. As with BUFFER-COPY, different field order and missing fields do not prevent the method from succeeding. There is also no requirement that indexes on the two temp-tables be identical.