As I understood, the RBI can not print and circular the money as it wish. First thing it can print money only against the old notes destroyed, it means that total currency rotation in the country shall be same always. The value of the currency (piece of paper) printed offset by keeping aside equal amount(or some percentage) of Gold in reserve in the Reserve Bank. It is mandatory. That is what the Govverner of RBI promises on the note that He will pay you the value of Rs............. so against present of that note. The reserve gold can not utilised by the Government for any other reason. So, in practical, there is a reserve of tons of Gold in the RBI against the money in circulation at present.
Same case applies to currency in all the Countries. That is the the reason, you can exchange your money to any foreign currency valued against the Gold price on the day. Otherwise, there is no way, you can exchange for foreign currency.
The Reserve bank can print the notes and keep in stock(That to for some ratio of total circulation in country may be around 3% and also to the extent it will get the old notes), but can not circulate it unless the sl. no. is registered in a registry, old note destroyed/gold reserve provided. Till the Note sl. No. enters in the registry, it will be piece of paper, but once it is registered it will get value and released for circulation. Sl. No. registration (in the book provided) is a critical stage of the release of currency, it is maintained since the rule of British, and still followed very carefully under very high supervision and security. It is like a "Praana prathistapana" for the Stone, which will become God.
In the present situation, everybody complain that, why the government has not printed enough notes for circulation, in advance, before demonitising it. In reality, the Govt might have printed(as per the ratio permitted), but it can not circulate till the old notes are reached back the RBI, registered once again, destroyed and allow new release. As fast as the people surrender their old money, that much fast the RBI releases the new notes.