>>513546294Well the "real money" has to be something the party that the bank is transacting to is willing to accept.
With the normie it will likely be cash, with the other banks, it will probably be central bank currency.
If it runs out of any of those it will be in a pickle.
In the case of central bank currency, which is the only case which seems realistic these days
it will usually take a loan from another bank, or the central bank will buy some bonds from the bank with the central bank currency.
As you can imagine, if there are no more bonds to exchange for central bank currency, there will be no more.(Unless of course the central bank has some kind of change of heart)
So in
>>513545293 Bank B has an issue at the very least.
But in case of a bank run, this will likely happen with cash.
So if in
>>513544880 A, B, C and D all withdraw their money, the bank would have to give them 8300.
But it only has 8000 reserves, so it can't pay it all.
The example was a pretty simplified though, so don't take it at face value ^^.
If we take the central bank into the game here, yes, there won't be much issue, the central bank will likely buy the loans and give the bank the necessary cash.
(Unless it wants to let the bank die that is).