Раньше я восстанавливал через

dbcc usedextents(dbid, type, display_opts, [bypiece])
или
dbcc usedextents(dbname, type, display_opts, [bypiece])

Option Description
dbid Database ID
dbname Database name
type Type of output:
Value info:
0 Display all used extents for dbid
1 Display used extents for log device (log must be on a seperate device.

device_opts Output Display format :
Value info
0 Display information about each extent
1 Display used and free extent counts

bypiece Display extent use for each database fragment in sysusages.
Value info
0 Do not display extent info per fragment (default)
positive value Display extent info per fragment

Run dbcc usedextents and recycle server. Incorrect free-page counts will be updated to the correct value in DBTABLE by running dbcc usedextents. However, sysusages wont be updated until ASE is recycled. Not recycling the server can result in discrepencies between dbcc usedextents and other space accounting utilities/commands. So, to get the most accurate and consistent statistics, run dbcc usedextents and immediately recycle the server

Но все равно через какое-то время опять появлялись отрицательные значения, так что я на это забил