The full length of a field whose value is NULL is no longer sent over the wire. (Tracker item CORE-2897). NULL flags (4 bytes per field) are replaced with a bitmap and only these flags are transmitted, in the bitmap.

This improvement is available for the DSQL API only, so gbak does not benefit from this improvement, as it uses a lower level BLR API.

The prefetch (batch receive) algorithm is now aware of variable-length messages, so that VARCHARs and NULLs may reduce the transmitted message size, allowing more rows to be transmitted in each batch.