either of the ends meaning in dbms code example

Example 1: dbms transaction tutorialspoint

Open_Account(A)
Old_Balance = A.balance
New_Balance = Old_Balance - 500
A.balance = New_Balance
Close_Account(A)

Example 2: dbms transaction tutorialspoint

Open_Account(B)
Old_Balance = B.balance
New_Balance = Old_Balance + 500
B.balance = New_Balance
Close_Account(B)