The Compiler creates a number of temporary work files. The size of them depends on the content of your program and the directives used, in particular the number of data and procedure names. The Compiler puts the files in the directory indicated by the environment variable. If this environment variable does not exist, the files are created in a system defined temporary directory, typically /var/tmp or /tmp.
The Compiler normally deletes these temporary files before it terminates. However if the Compiler terminates abnormally, for example due to machine failure, it might leave these files on disk. You can delete them, unless the Compiler is running in another session.
Before compiling, you must ensure there is enough free space for these temporary files in the appropriate directory.