Yes, Jose I found the issue. I had posted similar query in "SAP Adaptive Server Enterprise Developer Center" forum as I saw similar queries there (SAP has not clearly defined which forum is for what!, earlier Sybase forums were better). I posted the answer there - Unable to install ASE 16 on AIX (Link - http://scn.sap.com/thread/3767674)
Basically my /tmp was nearly full - 98%, so there was no space for installer to keep tmp files. Looks like it needs a lot of space. Secondly I cleaned up the whole $SYBASE directory having ASE files from my earlier attempt at install.
Regards
Amal