Two joint holders attempted simultaneous transfers of Rs. 10000 each. Both read Rs. 11000 balance. A was debited only once (final balance 1000). Which properties were violated?

The correct option is Consistency.

To understand why the consistency property is violated, let us analyze the scenario step-by-step:

1. Understanding the Consistency Property (C in ACID):
Consistency ensures that a database transition takes the database from one valid state to another, preserving all system invariants, integrity constraints, and business rules (for example, the total money transferred must equal the total money deducted from accounts).

2. Analyzing the Scenario:
Let the initial balance in the account be:
$\mathrm{Initial\; Balance}=11000$
Two joint holders simultaneously attempt to transfer Rs. 10,000 each. Both read the same initial balance of Rs. 11,000. Let the two transfers be represented by transaction T₁ and transaction T₂.

3. The Mathematical Discrepancy:
If both transfers are processed, a total of Rs. 20,000 is sent out of the system. The mathematically expected final balance of the account should be:
$\mathrm{Expected\; Balance}=11000-10000-10000=-9000$
However, the system debits the account only once, resulting in a final balance of:
$\mathrm{Final\; Balance}=11000-10000=1000$

4. Conclusion:
Because the account was only debited once (Rs. 10,000) while two separate transfers of Rs. 10,000 were executed, Rs. 10,000 has been created out of thin air. This violation of the fundamental rule of balance conservation breaks the integrity of the data, which directly violates the Consistency property.