documentclass[parskip=half,10pt,twoside]{scrbook}

begin{document}
chapter*{Introduction}
addcontentsline{toc}{chapter}{tocEntry{Introduction}}
markboth{spacedlowsmallcaps{Introduction}}{spacedlowsmallcaps{Introduction}}

chapter[Short title]{Full title}
 renewcommand{chaptermark}[1]{%
markboth{thechapter. #1}{}}

end{document}