Find out if a database is being used and how much

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Find out if a database is being used and how much

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jmanly

Posted Wednesday, April 23, 2008 3:45 AM

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Hi all,

Do you think it is possible to use DMVs (or DMFs) to find out if a database is being accessed by users or applications? For example, I wondered if I could use sys.dm_db_index_usage_stats to work out if a database has been used lately at all. The results are possibly getting distorted by system processes, because I am getting last_user_seek or last_user_scan, etc. populated in some (non-system) tables very recently although I know that no users connections have been in the database. Perhaps the plan is flawed from the start, since reindexing and other maintenance jobs would presumably increment the scan counters, etc.

Has anyone else tried anything like this? Or does anyone know of a useful DMV for this purpose? Maybe a DMV that consolidates login info?

Basically, the problem I am trying to solve is I am being asked "is anyone accessing databases x,y,z and, if not, you may delete them!". Other than running profiler for a few days, I love to know if SS 2005 consolidates this info somewhere.

Many thanks.
James

Post #489149

John Mitchell-245523

Posted Wednesday, April 23, 2008 4:01 AM

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James

If you suspect the databases aren't being used at all, then run a Profiler trace against them for a week or a month or however long you need to. If you see no activity, set them to restricted user and leave them like that for the same period of time. If nobody squeals, take a final backup and remove the databases.

John

Post #489156

Grant Fritchey

Posted Wednesday, April 23, 2008 6:19 AM

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I don't think there is one that tracks connections historically. If you really don't want to run Profiler, you might try running queries against sys.dm_exec_query_stats and see if any queries have been run against the database in question. That's about the best that I know of.

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Post #489207

jmanly

Posted Wednesday, April 23, 2008 9:57 AM

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Thanks, these seem sensible suggestions for me to try. It's also useful to know there's no really obvious script possible so i can stop trying!

Cheers.
James

Post #489394

GilaMonster

Posted Wednesday, April 23, 2008 12:27 PM

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I'd say use the dm_exec_query_stats. I believe there is a DBID in there. The plan cache is transcient, so commands may get removed from the cache and not all statements are cached at all.

Gail Shaw
Microsoft Certified Master: SQL Server 2008, MVP
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

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Post #489493

jmanly

Posted Thursday, April 24, 2008 5:10 AM

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Oh yes, thanks. If you CROSS JOIN the sys.dm_exec_query_plan DMF to sys.dm_exec_query_stats you get a dbid. A bit of experimenting reveals that ad hoc plans don't seem to expose a dbid in sys.dm_exec_query_plan if the query is ad hoc as opposed to a stored procedure, but the stored proc query plans do give you a dbid, so this is something to work with.

So, so far I have the following if anyone is interested:

WITH last_query_by_db (dbid, Last_query) AS (
select
dbid, max(last_execution_time) 'Last_query'
from
sys.dm_exec_query_stats
cross apply
sys.dm_exec_sql_text(plan_handle)
group by
dbid
)
select
d.name, Last_query
from
sys.databases d
left outer join
last_query_by_db q on q.dbid = d.database_id
where
d.name not in ('master','msdb','model','tempdb')
order by
1

I think - but could be wrong - a database that has only ad hoc queries executed against it would appear (incorrectly) from these results to not be used, but i don't suppose this includes too many production systems.

Bit of a work in progress at the mo!

Many thanks.
James

Post #489800

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