If you want to start SAP and Database automatically after OS start follow below steps.
If you are on HANA Database the below steps applies.
Create after.local file with below content in /etc/init.d location
su – hdbadm -c “/usr/sap/HDB/HDBxx/HDB start””
su – sapsidadm -c “/usr/sap/SID/SYS/exe/uc/linuxx86_64/startsap”
This script will run after all run levels are completed.