A system for supporting a transactional system in a heterogeneous computing environment, comprising: one or more microprocessors; one or more records buffers (105, 201) in the transactional system, wherein said one or more record buffers operate to store a representation of one or more data structures stored in a mainframe computing environment in the heterogeneous computing environment; and a transactional adaptor running on the one or more microprocessors, wherein said transactional adaptor operates to convert one or more data elements between said one or more data structures stored in the mainframe computing environment and said one or more record buffers in the transactional system, wherein the transactional system operates to use one or more transactional buffers that are based on one or more transactional data types and to convert said one or more data elements between said one or more record buffers and said one or more transactional buffers; wherein said transactional adaptor operates to use a tree structure to represent said one or more data structures in the mainframe computing environment; wherein the transactional adapter is configured to: generate a record description file from the one or more data structures; compile, from the record description file, a record object file in binary format as a serialised tree to maintain the tree structure in representing the one or more data structures; and wherein the transactional system is configured at runtime to access and manipulate the record buffers using the record description file. one or more microprocessors; one or more records buffers (105, 201) in the transactional system, wherein said one or more record buffers operate to store a representation of one or more data structures stored in a mainframe computing environment in the heterogeneous computing environment; and a transactional adaptor running on the one or more microprocessors, wherein said transactional adaptor operates to convert one or more data elements between said one or more data structures stored in the mainframe computing environment and said one or more record buffers in the transactional system, wherein the transactional system operates to use one or more transactional buffers that are based on one or more transactional data types and to convert said one or more data elements between said one or more record buffers and said one or more transactional buffers; wherein said transactional adaptor operates to use a tree structure to represent said one or more data structures in the mainframe computing environment; wherein the transactional adapter is configured to: generate a record description file from the one or more data structures; compile, from the record description file, a record object file in binary format as a serialised tree to maintain the tree structure in representing the one or more data structures; and wherein the transactional system is configured at runtime to access and manipulate the record buffers using the record description file. generate a record description file from the one or more data structures; compile, from the record description file, a record object file in binary format as a serialised tree to maintain the tree structure in representing the one or more data structures; and wherein the transactional system is configured at runtime to access and manipulate the record buffers using the record description file.