Parameters are essential elements of any database instance. They help us achieve required performance goals or define the behaviour/characteristics of instance.
Some parameters can be tuned while the database instance is running and some need to be adjusted while the instance is down. Therefore, beforehand knowledge of these parameters tuning scope is a handy tool for a DBA (Database Administrator).
In OneDB, we can classify parameters as static or dynamic:
The static parameter must be set with the instance stopped, editing the onconfig file, and starting the OneDB. If the onconfig is edited with the instance initialized, the parameter will only take effect after the database server is shut down and restarted.
However, dynamic parameters can be changed using the onmode utility while the server is online.
Dynamic parameters can be further classified as Persistent and non-persistent:
Persistent: can be changed in only onconfig (use onmode -wf only)
Non-persistent: can be changed in file and memory ( onmode -wf/wm both)
How to update parameters dynamically:
onmode -wf –> will update in onconfig and memory
onmode -wm –> will update only in memory
In OneDB we can check the nature of parameters by using onstat -g cfg
Here is the list of all the options of onstat -g cfg
cfg == basic info: name and current value of all params
cfg <name> == basic info for the given parameter
cfg full == all info, all params
cfg tunable == params that can be changed on the fly
cfg diff == params that have been adjusted or modified
cfg msg == params that generated a warning or error message
Regarding the onstat -g cfg :
- type, data type for the value.
- maxlen, max length of the value.
- units, in which the value is expressed.
- rsvd, indicates (with an asterisk) that the configuration parameter and its value are stored on the configuration reserved page.
- tunable, shows (with an asterisk) that the configuration parameter can be tuned dynamically, for example, with an onmode -wm or -wf command.
- min/max, the lower and upper limit that the value can be set.
- description, text explaining the parameter and the values it can have.
Below are the examples of using this utility.
- To get list of all tunable parameters:
onstat -g cfg tunable
- All details of an onconfig parameter –> onstat -g cfg full <parameter_name >
Static: (tunable –> blank)
Dynamic: Persistent (tunable –> persistent only)
Dynamic: Non-Persistent (tunable –> *)