dear sir
we do not have huge I.T set up and we have only one real time server the system is highly updated with 2gb ram and 160 dual hdd with single processors on that we have oracle database as well as we are using same system for backing up database we do not have any specific back up server all the back up which we are taken of database are there on real time server so we want to know the best practice of backing up our database so in case if we face any problem we can able to get full recovery of data awating for your co operation

You can create a second small database to act as a rman repository(put it all on a single filesystem) and use RMAN to back up your database (and 1 -2 days of archivelogs) to disk.

Once the rman backup of your primary database is done, shut down the small database and back up it to tape as a cold backup along with the backup set produced by the rman job.

Run this 2 times a day, keep one copy on site and send one off for DR.

No downtime of your primary database required.