In a database system,within a banking system application,transaction between A is transferring 1000 from Acc1 to account Acc2 at the same time,transaction B is processing every records and adding interest payment by increasing each balance by 1.5 percent initially Acc1 has a balance of 4000 and Acc2 hasa balance of 5000,read Acc1 record and lock, reduce the balance by 1000,write balance, release lock.

To understand and explain the process described, let's break it down into steps:

1. Reading Acc1 Record: The first step is to retrieve the record for Acc1 from the database. This involves executing a SELECT query on the database table that contains the account information. The query would typically include a condition to select the record for Acc1.

2. Locking the Record: Once the record for Acc1 is fetched, it needs to be locked to prevent any other transaction from accessing or modifying it. This is done to ensure data integrity and avoid conflicts when multiple transactions are updating the same record simultaneously. Locking is usually implemented using database-specific mechanisms like row-level or table-level locks.

3. Reducing the balance by 1000: After the record is locked, the balance of Acc1 needs to be reduced by 1000. This can be achieved by updating the balance field of the Acc1 record with the new value (4000 - 1000 = 3000). The update query would be executed on the locked record.

4. Writing the Updated Balance: Once the balance is updated, the modified record needs to be written back to the database to permanently store the changes. This is done by executing an UPDATE query that updates the Acc1 record with the new balance value.

5. Releasing the Lock: After the updated record is written, the lock on Acc1 needs to be released so that other transactions can access it. This ensures concurrency and allows other operations to proceed on Acc1.

It's important to note that the described process only covers the transaction involving Acc1. The transaction involving Acc2, which adds interest payment by increasing each balance by 1.5 percent, is not mentioned in detail. However, a similar approach of reading the Acc2 record, locking it, updating the balance, writing it back, and releasing the lock would be followed.