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To stay in tune with how your database performs, you need to pay close attention to the logs it generates.
Logs contain all sorts of handy info about how your data is being handled from moment to moment, and delving into them can give you insights into issues and optimization opportunities.
All this means that you need to learn how to read and interpret the information contained within SQL logs if you want to implement improvements and gain tangible benefits as a result. So here is an introduction to the world of logs and what they involve in a database context.
Getting to grips with error logs
The most useful type of log generated by SQL Server is an error log, which will point you towards any problems that have arisen for obvious reasons.
All good database management systems will come with log viewers, allowing you to quickly retrieve and review recent error logs, so long as permissions are set correctly to allow for this.
There are many different types of errors that can be detected and recorded in this way, and you can even search for something specific within this if you wish.
The main things to note when reading any type of error log are the date and time at which it occurred and the table within the involved database. This will help you to narrow down your search when troubleshooting and save a lot of time and effort in the process.
Understanding common errors
In terms of the kinds of mishaps that can occur within an SQL database, there are many issues that logs will document and describe, as mentioned. Being familiar with the main points of conflict that can arrive is half the battle.
Deadlocking is an excellent example of this, as explained over on SentryOne.com. Briefly, a deadlock arises if multiple processes have exclusive locks on database resources and are prevented from completing because control of the resources cannot be relinquished.
This might sound complex, but it is somewhat straightforward when you dig a little deeper and is also fundamental to how an SQL server preserves the integrity of data contained within it.
The fundamental problem with this kind of error is that it is an indication that the server is doing its duty. It is the administrator’s job to determine whether or not deadlocks have reached problematic, performance-compromising levels through monitoring and analysis.
Exploring other logs
Another aspect of reading SQL logs is knowing that while not all will be flagged as errors, some may still hint at problems creating a performance penalty and thus need to be dealt with.
The wait statistics relating to queries and processes can be considered relevant in this context. Knowing how long it takes for threads to gain access to resources can let you know whether there is room for optimization or whether locking privileges may be wrongly implemented at the moment.
Once again, with experience and training, you will be better equipped to sort the problematic wait stats from those that are entirely normal and essential to how the database functions.
Of course, different database solutions use SQL, and the logs recorded and made available to admins will vary from platform to platform.
For example, Microsoft’s SQL Server has a log viewer within its management service that also includes Windows events, giving you insights into whether the OS may be responsible for performance woes.
Making use of tools to improve efficiency
It is entirely possible to manually trawl the logs created in their thousands by your database, but this is hardly the most efficient approach.
Clever use of log viewers and the option mentioned above to narrow the range shown according to what you believe is the issue can help. However, this is still a potentially time-consuming and frustrating experience, which luckily can be avoided altogether.
This is where a separate database monitoring solution will be a blessing. The latest platforms can keep tabs on every transaction your server completes and alert you to the issues identified automatically.
From blocking and deadlocking to query conflicts and even security concerns, monitoring tools let you scrutinize and analyze your database in less time and with greater precision.
If you are a database admin, SQL log files are an asset that should not be left unexploited. From keeping up with regular monitoring and maintenance duties to dealing with the root causes of unplanned downtime, reading and interpreting logs will put you one step ahead of the game at all times.
Taking this a step further and using software tools to your advantage will iron out all sorts of obstacles, so don’t overlook them!