echo "---------------------------------------" >> ./backup_logs_$ORACLE_SID_{log_date}.log
should be
echo "---------------------------------------" >> ./backup_logs_$ORACLE_SID_${log_date}.log
As always, take babysteps in the beginning so start by echoing the intended output of the variables:
echo "backup_logs_$ORACLE_SID_${log_date}.log"
Now you can see that maybe the ORACLE_SID variable is not set at all.
I don't know ORACLE_SID, the way you're using it suggests it should be set in your environment ...
I'm not sure but if the file does not exist beforehand it might be better to create it first by using:
Code:
touch ./backup_logs_$ORACLE_SID_${log_date}.log