Automated Server Information Gathering – Part 1

Introduction

There is a great deal of information about
your
SQL Server that may be of interest to you or your clients. I was
recently asked how to gather some statistical information for a SQL Server
and
its environment by a client. The person asking the question was wondering
whether to use Performance Monitor, stored procedures, or some other method
to get the
following information:

  • #
    users connected to each database
  • name of
    all databases
  • size of
    each database on disk (physical size)

Most of this information can be gathered
using
Performance Monitor, with the exception of the first item. Performance
Monitor provides
total users connected to the server, but not by database. In addition, if a
new
database is added, the Performance Monitor chart or log settings must be
altered to add the
new database instance to the database size object.

I do use Performance Monitor heavily to
monitor my
database servers and see how they are performing. There are a number of data
points that performance monitor provides that I cannot get from another
source.
There are a large number of articles written on how to use performance
monitor
and quite a few specific to SQL Server, so I will not delve into details
here
(If you need more information on Performance Monitor, see Brad
McGehee’s series
on this topic). I
view Performance Monitor more of a long term trending tool than a status
tool as
it is cumbersome to get the data from Performance Monitor into a format that
is
easily used (At least, for me it is a cumbersome process).

So that brings me to this article. I like
getting
a daily status from my servers. A quick, concise view of what has happened
on
the server over the last day. I try to keep this information to a minimum as
I
do not have the luxury of being able to examine in detail how my servers are
doing everyday. Instead I only want errors or exceptions reported to me. The
less information I see everyday, the better. Of course I like to keep track
of
things, but information management to prevent information overload is
becoming
more important as the number of servers grow in my organization.

What kind of data can we gather?

So, lets get started. How can I get
information
from my SQL Server? Well, let’s pick a few data items to gather. How about
the
following list my client asked for?

  • Total
    users per database
  • Total size of each database
  • Last
    Backup of each database

This is a pretty general list, though I would
not
usually get the last backup on my servers. Instead, I would have some task
that alerted me if
there was a problem with a backup, but for the example let’s use this list.
I
will tackle these items one by one. This article will tackle item # 1 with
#s 2
and 3 in follow-up articles.

Total Users Per Database

This is an interesting one, because the
number of
users in a database is a snapshot statistic. The number of users is only
meaningful at some point in time because users log in and out of databases
constantly. In order for this to have some meaning you want it to include a
time
stamp of when the count was made.

So, I still have not answered where we can
get
this information. Microsoft has a couple of ways in which this can be done.
The
recommended way to find out about users and databases is to use the sp_who
or
sp_who2 stored procedures. These procedures return a list of all users and
the
databases they are connected to. However, in order to get a count by
database,
we would need to trap this information in a temporary table and then run a
query
to select the information out of this table. The code for doing this is
given
below:

create table #users (
       spid int,
       status char( 40),
       loginname char( 100),
       hostname char( 100),
       blk int,
       dbname char( 40),
       cmd varchar( 200)
       )

     -- load the table
     insert #users
      exec sp_who

     -- get the totals
     select dbname,
            count(spid)
      from #users
      group by dbname

     drop table #users

Many people will realize that you could just
as
easily get this information by querying against sysprocesses in the
following manner:

select d.name,
            count(spid)
      from sysprocesses s, sysdatabases d
      where s.dbid = d.dbid
      group by dbname

This seems shorter and cleaner, so why not do
this? Well, I used to do this quite often in v6.5 to generate daily status
information. When v7.0 was released, a number of my stored procedures
stopped
working after an upgrade. After digging in further I found that the
structure of
some of the system tables changed. As a result I was no longer getting the
results that I expected, and in some cases the procedures would return
errors.

MORAL: If you can possibly avoid it, do not
use
the system tables for queries. There is no guarantee that these will remain
the
same over time. Instead, Microsoft has done a good job providing views and
stored procedures which you can query for information about the
server.

Enhancements

The code batch above will return a snapshot
of
the count of users per database when it is run. However, I think this is of
limited use. So here are a few enhancements that I would make to this
batch. First I would make it a stored procedure so I can schedule it easily
using the SQL Agent. I feel that if there are any scripts that you run on a
regular basis, you are better off creating stored procedures out of them.
This
gives you a building block for stringing processes together.

My client wanted to know two things about
this
data. The maximum count of users for each database for the previous day, and
a
long term average. So next I would create a table in which to store the
data.
That way I could query this each day for the previous days maximum as well
as
store this for long term trends. This changed the query statement as shown
below:

insert dbusage (dbname, usrcnt, entrydt)
      select dbname, count(spid), getdate()
       from #users
       group by dbname

To get the daily report back, we setup a
procedure to send the results of the following query through email to the
administrator:

select dbname,
            max( usrcnt) 'User_Count'
      from dbusage
      where entrydt > dateadd( day, case when datepart( dd, getdate()) = 2
                                         then -3
                                         else -1
                                   end, getdate())
   group by dbname

This returns the previous days (or previous 3
days if monday) count per database.

Now we can schedule the first code to run
every
minute or so during the day and store the information. There is a flaw in
this
system in that if a user logs in and then out of the database between
executions
of the task, we will not count them towards our maximum. I think this is a
small
price to pay given that if our performance monitor interval were long
enough,
say 30sec, the same thing could happen. We can also schedule the second code
to
run every business day at the same time so that the intervals between
reports is
consistent.

Next time I will tackle gathering the size of
every database on the system dynamically.


Steve Jones
September 2000

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