Subject garbage collection points
Author Tomas

I studied good article about FB on this thema
(, and from
articles on IBSurgeon pages), but I have still some small questions
about. I will be glad of anybody's help.

1. From header page info:
Oldest transaction - known as Oldest Interesting Transaction (first
transaction in other state then commited)
Oldest active - Oldest transaction currently active
Oldest snapshot - known as Oldest Active Transaction (transaction
what was active when current Oldest active transaction was run)
Am I understand header page info correctly ?

2. If an transaction is rollbacked, it will be changed to commit state
later by sweep process. Before it happen, do other transaction suppose
to clean its' garbage (garbage of rollbacked transaction) ?
I suppose cooperation mode in garbage collection.

3. Is garbage collection process (again suppose cooperation mode) on
record trigered only by SELECT statement or it could be trigered aswell
by UPDATE or DELETE statements ?

4. OIT and OAT transaction numbers on header page are updated only just
in time when transaction start and will find out, that OIT and OAT are
not actual ? So this transaction pickup new values into her local
variables and will try to actualize header page ?

thanks, tomas