Message file descriptors

By default ESQL/C frees all file descriptors for a message file when it closes the message file. As a performance optimization, however, you can set the environment variable IFX_FREE_FD to cause to not free the file descriptor if the message file being closed is open for another thread. If you set IFX_FREE_FD to 1, frees the message file descriptor only for the thread that closes the file.