Hi guys i'm quite new to db2 who can help how do i know from the backup image file which platform it was taken from say unix,windows or i5os. thanx

Try db2ckbkp

Just to add:

db2bkckp -H will give you the following information (this is from 64-bit AIX):

Platform -- 14


This value is in hex, convert it to dec and then look up the platform name in .../sqllib/include/sqlmon.h


For my example:
#define SQLM_PLATFORM_AIX64 20 /* AIX 64 bit