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Find out if a database is being used and how much


Find out if a database is being used and how much

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Jimmy M
Jimmy M
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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
John Mitchell-245523
John Mitchell-245523
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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
Grant Fritchey
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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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Jimmy M
Jimmy M
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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
GilaMonster
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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
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SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

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Jimmy M
Jimmy M
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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
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