MySQL database backup was less than 2MB, but Oracle XE backup of the same database is about 1GB
I don't know if the two backups are comparable, but with backup.sh script you won't ever have a so small backup : it makes a full RMAN backup, and to reduce the backup size you have two choices :
1. Modify the script so that it does a compressed backup
2. Create your own script.
Said that I obviously prefer #2, if you want to modify the script, you can change all lines with "backup as backupset device type disk database;" to "backup as compressed backupset device type disk database;"
FYI, the difference, for my XE database, is as follows :
-rw-r----- 1 oracle dba 790650880 6 lug 15:25 XE_07oe2pan_1_1.bck
-rw-r----- 1 oracle dba 9830400 6 lug 15:25 XE_08oe2pb6_1_1.bck
-rw-r----- 1 oracle dba 176455680 6 lug 15:32 XE_comp_09oe2pnl_1_1.bck
-rw-r----- 1 oracle dba 1097728 6 lug 15:32 XE_comp_0aoe2poo_1_1.bck