To workaround the problem you may use the following script. The script will delete sessions history but it will keep the information about last 1000 session from the database.
@bsess as table([id] uniqueidentifier)
insert into @bsess(id)
select b.id from BSessions b where b.id not in
select top 1000 id from BSessions order by creation_time DESC
where session_id in (select id from @bsess)
where id in (select id from @bsess)
To run the script you may use SQL management studio or you may also follow next steps:
1. Stop Veeam services
2. Save the file to any file, "script.sql" for example.
3. Run the following command: sqlcmd -S COMPUTER\INSTANCE -d VeeamBackup -i
PATHTOSCRIPT\script.sql -o c:\resetresult.txt
where COMPUTER is the name of computer with database, INSTANCE is the name of instance (VEEAM for default installation), PATHTOSCRIPT is the path to the script.
4. Start the services