SIP stands for Systematic Investment Planning, and it is a method of investing that allows you to invest a set amount at regular intervals (weekly, monthly, quarterly, etc). Stocks can also be purchased using SIPs.

You won't have to worry about manually placing orders at regular intervals, once you've set up a SIP. If you have adequate cash in your trading account, the system will automatically place your orders
Please keep in mind that the money for your SIP is debited from your Trading account, so make sure they are available on the SIP day.

The SIP order may fail if the requisite funds are not available in your trading account on the given date.

You can use the e-Mandate facility to guarantee that your trading account has enough funds.

You can use the e-Mandate feature to have a certain quantity of money sent from your bank account to your trading account on a specific date.