Progress
Programming
Handbook


How Progress Applies Locks

You’ve just seen how you can apply a lock on your own. But if you do not apply any locks, Progress performs default locking. In particular:

NOTE: SHARE–LOCKs and EXCLUSIVE–LOCKs use up entries in the lock table. The possible number of entries in the lock table defaults to 500. You can change this with the Lock Table Entries (–L) startup parameter. Progress stops a user program if it attempts to access a record that overflows the lock table.

In Figure 13–3, when the FIND statement reads the customer record, Progress puts a SHARE–LOCK on that record. Because the UPDATE statement lets you change the record, Progress upgrades the SHARE–LOCK to an EXCLUSIVE–LOCK after the UPDATE statement executes.

p-lock3.p

Figure 13–3: How Progress Applies Locks


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