At a high level the JDBC Adapter will allow upstream apps to query RDBMS data over JDBC and get the JDBC objects converted to Arrow objects/structures. The upstream utility can then work with Arrow objects/structures with usual performance benefits. The utility will be very much similar to C++ implementation of "Convert a vector of row-wise data into an Arrow table" as described here - https://arrow.apache.org/docs/cpp/md_tutorials_row_wise_conversion.html
The utility will read data from RDBMS and covert the data into Arrow objects/structures. So from that perspective this will Read data from RDBMS, If the utility can push Arrow objects to RDBMS is something need to be discussed and will be out of scope for this utility for now.