<<I found a strange issue when sweep is executed.

I'm using Firebird 2.5.2 Super Server for Linux AMD 64 bits.

I first execute "SHOW DATABASE" in isql:

PAGE_SIZE 16384
Number of DB pages allocated = 524480
Sweep interval = 20000
Forced Writes are OFF
Transaction - oldest = 26483174
Transaction - oldest active = 26483175
Transaction - oldest snapshot = 26483171
Transaction - Next = 26483367

Shortly after, I do a manual sweep to the same database. This lines
appear in firebird.log:

Sweep is started by SYSDBA
Database "path_to_databse.fdb"
OIT 26489872, OAT 26489873, OST 26489873, Next 140660205433875

As you can see, it seems to be a huge gap between next transaction and
the other values.

I guess that is not true, as just some minutes went on from measured
points.

Is it a normal behaviour?>>

No its a bug
http://tracker.firebirdsql.org/browse/CORE-3978

Regards
Paul