How can I access SDL logs?

Use this link:
http://server:port/sld/admin/log.jsp

I got error message "SLDAccess set to true, but not available".

Go to SLD:
http://server:port/sld/ListServlet?bsview=true
Business systems and check if your XI business system has correct "Pipeline URL" parameter defined:
http://server:httpport/sap/xi/engine?type=entry
also check TCODE -> SLDCHECK - if you don't have any errors over there