Hi Divya,
To get _SYS_AFL Schema in your system, you will have to install AFL(Application Function Libraries)
You can check HANA PAL Guide, it says, install AFL first:
http://help.sap.com/hana/SAP_HANA_Predictive_Analysis_Library_PAL_en.pdf
To install AFL, Check the HANA Installation Guide:
http://help.sap.com/hana/SAP_HANA_Server_Installation_Guide_en.pdf
Also check this thread for installation:
http://scn.sap.com/thread/3276681
To use PAL and BFL, you need to have AFL installed in HANA.
Regards,
Vivek