dbscontrol is a utility in Teradata which is helpful in tuning the system level configuration of Teradata. These are normally accessible via the Linux console of Teradata and we should be very careful and sure before making any changes to the same as any wrong change can severely impact the database performance.
There are 100s of dbscontrol parameters and here we will discuss how to invoke dbscontrol utility and information about few of the mostly used dbscontrol parameters.
There are 2 ways of invoking the dbscontrol utility
– Through the Linux Console
– Through cnsterm supervisor window
You can directly invoke it from Linux console by going on the PDN node (control node) and typing dbscontrol. It will open the dbscontrol utility and wait for a command from you.
Another way of doing the same is through supervisor window, which is invoke by typing cnsterm 6 on the PDN node, and then typing ‘start dbscontrol’. It doesn’t matter which way you invoke the utility, you will be asked for dbscontrol commands once the utility has been invoked.
There are different group of system level tunables in dbsconrol
Also, the different kinds of commands of dbscontrol are DISPLAY,MODIFY,WRITE,HELP,QUIT
So, typing display general will show you the general fields of dbscontrol. modify general <field number> will modify the parameter. Same is the case with ther group of tunables as well. I will not be posting a sample output as there are a number of parameters and it will take up a lot of space . You can try and let me know if you face any issues.
Below are some of the basic fields/tunables that we end up modifying on need to basis.
– MaxParseTreeSegs: It is the maximum number of parse tree segments that the parser allocates while parsing a request. The default value of this parameter is 3000 but with more complex queries we will have to raise it to a higher value close to 10000 otherwise our complex queries start failing with the following error.
3712 Insufficient memory for Plastic Steps for this request. We will learn more about what are plastic steps and concrete steps in future artciles.
– MaxDownRegions: This defines the maximum number of down regions allowed before a table is marked as down. We will discuss more about the down regions and down table in the next aticle
– DeadlockTimeOut: This is the time in seconds between the cycles that Teradata checks for a deadlock. When a deadlock is detected, Teradata aborts one of the sessions
– RollbackPriority : Determines if the roll back runs on the highest priority or not.
Above are few that we normally use but please be aware there are 100s of such fields that completely control how the system behaves. Chaging some of them might require a database restart to take affect.
That’s it for dbscontrol parameters. Do comment if I can clear any of your questions.