The Oracle Linux installation works fine, but you have not configured your system properly. Perhaps you removed the drive where you stored the Grub configuration menu and files, or you use an invalid partition setup. Since you are not giving any information about your computer setup, partition layout, or how you installed the system, further help is not possible. Btw, there is no OEL, the product is called Oracle Linux or OL.
A boot partition of 200 MB is too small. I suggest to use at least 512 MB, which is the default. When you reinstall the system, make sure to replace the default master boot record (MBR) of sda and install GRUB to the /boot partition, usually sda1. Note that /boot must be a primary partition and not extended (logical), which might be the case if you use any (obsolete) existing dual-boot configuration.