In SAP, parameters are used to set the configuration and define the functionality of an sap system like number of workprocesses, buffer size, locktable size etc.
Basically there are 2 types of parameters :
Static are the parameters those won't take effect immediately the value is set. Restart of an sap system is required for them to take effect.
Dynamic are the parameters those will take effect immediately in the run time. Restart of an sap system is not required for them to take effect.
Parameter can be differentiated whether it is dynamic or static by checking in RZ11 transaction of SAP.
In Rz11, type the parameter and display it. In the screen , there will be a check box with description as "Dynamically switchable". If that check box is ticked, it means that it is dynamic parameter and value can changed in run time without restart of the system. If it is not ticked, then it is static parameter and it needs restart of a sap system for the changes to take effect.