SAP parameter can be set using RZ10 transaction. Go to RZ10, select the respective instance profile of the application server on which you would like to change the parameter.
From the dropdown of profile, select the instance profile (of the application server) on which you would like to change the parameter.
After selecting the profile, select extended maintenance button and press change push button.
It displays a screen with all the parameters as shown below :
You can either search the parameter or create the parameter and then set the value to the desired and save the same as below.
Set the parameter value in the text box provided and click copy button to copy the same and then press back button and press copy again in the next screen. After that press the back arrow to come to the following screen
Click on Save button to save and activate the profile.
Press no to goto the next screen
Press yes, to activate the profile.
The parameter will take effect after restart of the application server