This depends on whether you are using SQL or Native.
In general LOCKTABLE 'expires' (the locks are released) when your transaction ends.
Your transaction can end in few ways:
1. a commit call
2. If you call a report, when the report returns
3. If you are on a form, (assuming default properties), one transaction ends/begins when you complete the primary key information. Another transaction ends/begins when you leave the form.
Comments
In general LOCKTABLE 'expires' (the locks are released) when your transaction ends.
Your transaction can end in few ways:
1. a commit call
2. If you call a report, when the report returns
3. If you are on a form, (assuming default properties), one transaction ends/begins when you complete the primary key information. Another transaction ends/begins when you leave the form.