Original side appeal?

Hello sir, greetings of the day.
OSA stands for Original Side Appeal. There are four chartered High Courts, they are Bombay, Calcutta and Madras, along with the Delhi High Court, which have Original Civil Jurisdiction over matters, that empowers them to hear civil suits in the first instance. Thus the High Courts have an original side and an appellate side. Speaking of the original side of Calcutta High Court, you can file a civil suit directly before the Calcutta High Court provided the required conditions are met. Generally, the District Courts and other subordinate civil courts are given the jurisdiction to entertain civil suits. But one can approach these four High Courts in an appeal. You cannot file a suit directly in any other High Court except these four. 
Hope this answered your question.
Regards
Nirali Nayak
Law Student