Give an example of a schedule at the READ COMMITTED isolation level in which a lost update occurs.
What will be an ideal response?
Suppose a transaction reads the value of an item, x, and, on the basis of the value read, writes a new value back to x. A deposit transaction in a banking system has this pattern of behavior, where x is the balance of the account being credited. At the READ COMMITTED isolation level, such a deposit transaction releases its read lock before acquiring a write lock, two deposit transactions on the same account can be interleaved as illustrated in the following schedule
r1(x) r2(x) w2(x) commit2 w1(x) commit1
The effect of T2 is lost since the value written by T1 is based on the original value of x, rather than the value written by T2. Thus if T1 was attempting to deposit |S5 and T2 was attempting to deposit |S10, the final database has only been incremented by |S5, so T2’s update has been lost.
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To include a calculated field on a form, most database developers create the field in a query, and then use that query as the record source for a form.
Answer the following statement true (T) or false (F)
Given that the user input for Response is 3, what would be displayed if code corresponding to the following program segment were run?
``` Input Response Select Case Of Response Case 1: Write “You’re a newbie” Break Case 2: Write “You’re Number 2” Break Case 3: Write “The door to Sesame Street is open!” Break Default Write “Huh?” End Case ``` a. You’re a newbie b. You’re Number 2 c. The door to Sesame Street is open! d. Huh? e. Nothing would be displayed since Response is not one of the conditions in the Case statement.
What are some ways EFS keys may be lost?
What will be an ideal response?
Standard code libraries in Java are called:
(a) Methods (b) Classes (c) Packages (d) Statements