For an SQL server to operate normally, a system called TempDB needs to be up and running behind the scenes.
Experienced DBAs will already know exactly what purpose TempDB serves and how it is of benefit to any SQL server setup, but if you are unfamiliar with its uses and importance, this quick introduction will bring you up to speed.
In the simplest terms, TempDB is a database within a database, or rather the infrastructure which underpins all of the databases that are contained within a given SQL server ecosystem.
Whenever temporary data needs to be stored while being used by applications, users or the database itself, TempDB is the place it resides.
This information is always transient, and will persist for as long as it is needed by a particular process, before being erased.
Essentially, without TempDB, it would be very difficult to keep an SQL server operational with any level of efficiency.
The data distinctions
The data which ends up in TempDB generally falls into a trio of key categories, briefly alluded to above. First there is data generated by users, then internal data created by the SQL server itself, and finally the version store, which is partly responsible for ensuring that notable data can be read rapidly even if multiple processes are trying to access it simultaneously.
It is worth noting that while TempDB does help with serving queries and keeping the information flowing to users, apps and other areas of the server infrastructure, it is not something you can backup in its own right. The data should persist until the session ends or the user disconnects, at which point it is dropped to make way for more transient data.
The performance perks
It is one thing to say that TempDB helps with SQL server performance and cause issues in this area if problems arise, but quite another to understand the intricacies of what this involves.
The most common of these complications relates to the way that storage is managed within TempDB, because of course if the available capacity is maxed out then it is not possible for new changes to be made, leading to app slowdown and other dilemmas that end users will notice.
Regular cleanup of TempDB can help with this, ensuring that there is adequate free space to keep up with demand.
Thankfully you can overcome sub-optimal performance if you correctly configure TempDB in the first place and also take steps to monitor it over time. This is of course only relevant if you are directly responsible for running the SQL server itself; if you are simply an end user and you are encountering performance issues, contact your DBA.
So there you have it; the goal of TempDB is to store transient data in an SQL server without getting overburdened itself. In that sense it is a little like system memory, and should be seen as a crucial component of any database, helping it to run smoothly.