Download lesson29

Troubleshooting Techniques
Lesson 29
Skills Matrix
Skill Matrix
Troubleshooting
• Develop a systematic approach to solving
problems: guessing rarely proves effective.
You have options:
– Dividing and conquering
– Tracking causes and effects
– Analyzing and deducing
Troubleshooting the Installation
• You need to know why your SQL Server
installation failed.
• The first place to look when you have problems
is in the Windows Event Viewer.
• If you do not find the source of your problems in
the Event Viewer, navigate to X:\Program
Files\Microsoft SQL Server\90\Setup
Bootstrap\LOG, open the Summary.txt file, and
check for error messages.
Troubleshooting SQL Server
• To fix a problem, the logical first step is to
determine the cause of the problem, and the
best way to do that is by reading the error
logs.
• Error logs in SQL Server are stored in two
places—the first is the SQL Server error logs.
• The second place you will find SQL Server
error messages is in the Windows
Application log.
Troubleshooting Blocks and Deadlocks
• Obviously, you do not want other users to be
able to make changes to data while you are
reading or modifying it yourself.
• To keep this from happening, SQL Server
automatically places locks on the data that
is being accessed to limit what other users
can do with that data at the same time.
• SQL Server has several types of locks;
shared locks and exclusive locks.
Shared Locks
• Shared locks are placed on data that is
being accessed for read purposes. In other
words, when a user executes a SELECT
statement, SQL Server places a shared lock
on the data requested.
• Shared locks allow other users to access the
locked data for reading but not modification.
Exclusive Locks
• Exclusive locks are placed on data that is
being modified.
• This means when a user executes an
INSERT, UPDATE, or DELETE statement, SQL
Server uses an exclusive lock to protect the
data.
• Exclusive locks do not allow other users to
access the locked data for any purpose; the
data are exclusively available to the user
who placed the lock.
Troubleshooting Blocks and Deadlocks
• SQL Server does a great job of dynamically
setting these locks, so you don’t need to be
concerned with setting them yourself.
• What you do need to be concerned with is
making sure your queries are properly
written so SQL Server does not place locks
that get in the users’ way.
• The primary cause of this is deadlocks.
Troubleshooting Jobs
• You can use jobs to automate tasks in SQL
Server.
• Jobs are actually a series of steps that occur,
one after the other, to accomplish a task.
Troubleshooting Jobs
• If one or more of your jobs are not working, check the
following:
– The SQL Server Agent service must be running for jobs to
work. If it is not, start it.
– Make sure the job, each step of the job, and each
schedule of the job is enabled.
– Make sure the owner of the job has all the necessary
permissions to run the job.
– Check the logic of the job; that is, make sure all the
steps fire in the correct order.
• You can tell easily whether a job has run successfully by
looking at the history to find out when the job last fired.
Dynamic Management Views
• Dynamic Management Views and functions return
server state information that can be used to monitor
the health of a server instance, diagnose problems and
tune performance.
• There are two types of dynamic management views
and functions:
– Server-scoped dynamic management views and
functions. These require VIEW SERVER STATE
permission on the server.
– Database-scoped dynamic management views and
functions. These require VIEW DATABASE STATE
permission on the database.
Information Schema
• The Information Schema provides the same
information as the system catalog views but
also provides a layer of abstraction making
the metadata more consistent and easier to
work with.
• Information Schema views are based on an
ISO standard and applications that use them
are portable to other database systems that
are also ISO compliant.
Performance Studio
• Performance Studio stores historical
performance data displayed in several
different reports.
• Examine these reports for clues to
performance degradation.
Event Logs
• Your operating system maintains the event
logs. For the most part you want to examine
the application log.
• Go to Administrative Tools  Event Viewer
 Windows Logs  Application.
• Scroll through the entries looking for,
primarily, red icons. Double-click the icon to
get a descriptive message box. Take
appropriate action.
Event Viewer
Server Operational Logs
• SQL Server maintains its own logs. Navigate
to SQL Server Management Studio 
Management  SQL Server Logs.
• Double-click the current log. Scroll through
the log to gain an understanding of what it
reports.
• Click on the magnifying glass (search). Enter
FILESTREAM. See how your system is
configured.
SQL Logs
SQL Server Profiler
• Microsoft SQL Server Profiler is a graphical
user interface to SQL Trace for monitoring an
instance of the Database Engine or Analysis
Services.
• You can capture and save data about each
event to a file or table to analyze later.
Operating System Performance
• SQL Server and Windows Server provide
hundreds a relevant counters to help you
decipher the state of your server.
• Use these counters to help you troubleshoot
your server’s problems.
• Use these counters to decide if more
memory will solve the performance issue; if
an additional CPU will help; if it’s really a
network slowdown.
Trace Flags
• Use trace flags to set specific server characteristics
or to switch off a particular behavior.
• In SQL Server, there are two types of trace flags:
session and global.
• Session trace flags are active for a connection and
are visible only to that connection.
• Global trace flags are set at the server level and
are visible to every connection on the server.
• Some flags can only be enabled as global, and
some can be enabled at either global or session
scope.
DBCC TRACEON and TRACEOFF
• To enable a trace flag globally use the Query
Editor and use the -1 argument:
DBCC TRACEON (2528, -1)
• To turn it off:
DBCC TRACEOFF (2528, -1)
Startup Options
• To enable persistent trace flags, use this
example:
sqlservr -T1807
• If you use a shortcut, right-click the shortcut
icon, choose Properties, and then change
the path setting appropriately.
Microsoft SQL Server Database Engine Tuning
Advisor
• Microsoft SQL Server Database Engine
Tuning Advisor helps you select and create
an optimal set of indexes, indexed views,
and partitions without requiring an expert
understanding of the structure of the
database or the internals of Microsoft SQL
Server.
Job Activity Monitor
• The Job Activity Monitor allows you to view
the sysjobactivity table by using SQL Server
Management Studio.
• You can view all jobs on the server, or you
can define filters to limit the number of jobs
displayed.
• You can also sort the job information by
clicking on a column heading in the Agent
Job Activity grid.
Activity Monitor
• Activity Monitor provides information of SQL
Server processes and how these processes
affect the current instance of SQL Server.
Non-Graphical User Interface
• Many less used tools have yet to be
converted to GUI displays.
• To perform these functions use the
Command Prompt of the operating system or
PowerShell included in SQL Server.
Single User Mode
• You may need to lock out users while you do
especially resource-intensive maintenance
tasks.
• Use PowerShell to run sqlservr –m.
SQLdiag
• The SQLdiag utility is a general purpose
diagnostics collection utility that can be run
as a console application or as a service.
• You can use SQLdiag to collect logs and data
files from SQL Server and other types of
servers, and use it to monitor your servers
over time or troubleshoot specific problems
with your servers.
Summary
• You also learned about troubleshooting
problems, which is important because all
systems will eventually have problems.
• You first learned where to find the SQL
Server error logs in Management Studio and
how to read them.
• You then saw how to find errors in Windows
Event Viewer.
Summary
• You learned about a new tool starting with
SQL Server 2005, the DAC.
• This is a special connection that is always
open and listening on TCP port 1434.
• It allows a single member of the sysadmins
server role to connect to an unresponsive
SQL Server to run simple diagnostic queries.
Summary
• You learned about troubleshooting blocks using the
sys.dm_exec_requests system view.
• This is a valuable skill because when a session is
blocked, it will never execute, and your users will not
be able to get their work done.
• After that, you learned how to find out when a job last
ran in Management Studio.
• It may seem simple, but this can save a lot of time
when troubleshooting problem jobs.
• This lesson also reminded you to use many SQL Server
applications and tools to help identify problems.
Summary for Certification Examination
• Get familiar with the DAC. The DAC is a special
diagnostic connection that is always available for
administrators to connect with.
• This special connection uses limited resources on
the server and is useful for running simple
diagnostic commands.
• You can use either sqlcmd with the -A switch, or
Management Studio with admin: in front of the
server name to connect to the DAC. Only one
administrator at a time can connect.
Summary for Certification Examination
• Know how to troubleshoot. Pick a technique.
Be rigorous in your approach.
• Use existing tools creatively.
• SQL Server answers when you know how to
ask. Listen. Solve.
• Keep your systems humming and your users
content.
Summary for Certification Examination
• Know the error logs and locations. SQL
Server logs errors in two places on the
server: the SQL Server error logs and the
Windows event logs.
• To find SQL Server errors in the Windows
logs, you need to use Event Viewer and look
in the Application log.
• The SQL Server error logs are best viewed in
Management Studio.
Summary for Certification Examination
• Know how to use sys.dm_exec_requests to
troubleshoot blocks.
• Blocks occur when one session has an exclusive lock
on an object that another session needs to use.
• If the blocking session does not let go of the lock, then
the second session will never complete.
• This causes problems for your users, so to find the
blocking session, you can query the sys.dm_exec_
requests system view and look specifically at the
session_id, status, and blocking_session_id columns.
Summary for Certification Examination
• Know when to use an available tool from
SQL Server's arsenal of troubleshooting
weapons. If Profiler is better for a specific
issue, don't pick System Monitor.