=========================== DCMTK ENVIRONMENT VARIABLES =========================== The behavior of the DCMTK tools and libraries can be modified by a number of runtime environment variables which are explained below. DCMDICTPATH Affected: dcmdata Explanation: On Unix platforms, all DCMTK applications load a DICOM data dictionary from file upon startup. By default, the file /usr/local/share/dcmtk/dicom.dic will be loaded. If the DCMDICTPATH environment variable is set, the applications will attempt to load DICOM data dictionaries specified in the DCMDICTPATH environment variable instead. The DCMDICTPATH environment variable has the same format as the shell PATH variable in that a colon (":") separates entries. The data dictionary code will attempt to load each file specified in the DCMDICTPATH environment variable. It is an error if no data dictionary can be loaded. On Win32 platforms, a built-in dictionary is used by default. If the DCMDICTPATH environment variable is set, the applications will attempt to load _additional_ DICOM data dictionaries specified in the DCMDICTPATH environment variable instead. The DCMDICTPATH environment variable has the same format as the shell PATH variable in that a semicolon (";") separates entries. The data dictionary code will attempt to load each file specified in the DCMDICTPATH environment variable. See also: documentation in dcmdata/docs/datadict.txt or /usr/local/share/doc/dcmtk/datadict.txt. TCP_BUFFER_LENGTH Affected: dcmnet Explanation: By default, DCMTK does not modify the TCP send and receive buffer length, i.e. the operating system is responsible for selecting appropriate values. If the environment variable TCP_BUFFER_LENGTH is set, it specifies an override for the TCP buffer length. The value is specified in bytes, not in Kbytes. If set to 0, a buffer length of 64K, which was the default value for previous versions of the DCMTK, is used. TCP_NODELAY Affected: dcmnet Explanation: If this environment variable is set and contains a non-zero number (e.g. "1"), the Nagle algorithm will be disabled for TCP transport connections, which might result in better network performance on some systems/environments, especially when many small network packets are to be sent. If it is set and contains the number "0", the Nagle algorithm will not be disabled. If the environment variable TCP_NODELAY is not set, the default behavior applies (see compiler macro DISABLE_NAGLE_ALGORITHM in config/docs/macros.txt or /usr/local/share/doc/dcmtk/macros.txt).