Marks a statement block as a critical section by obtaining the mutual-exclusion lock for a given object, executing a block of statements, and then releasing the lock.
Example
class-id Account.
working-storage section.
01 balance binary-long.
01 r type Random value new Random.
method-id new.
procedure division using value init as binary-long.
move init to balance
end method.
method-id Withdraw.
procedure division using value amount as binary-long returning ret as binary-long.
*> This condition will never be true unless the lock statement
*> is commented out:
if balance > 0
display "< 0"
raise new Exception("Negative Balance")
end-if
sync on self
if balance >= amount
display "In critical section"
*>display "Balance before Withdrawal : " balance
*>display "Amount to Withdraw : -" amount
compute balance = balance - amount
*>display "Balance after Withdrawal : " balance
move amount to ret
else
display "In critical section"
move 0 to ret
end-if
end-sync
end method.
method-id DoTransactions.
local-storage section.
01 i binary-long.
procedure division.
perform varying i from 0 by 1 until i = 100
invoke self::Withdraw(r::Next(1, 100))
end-perform
end method.
end class.
