Changing DB user password

Hello,

Due to some security reasons we are planning to change the ALM user passwords.

I went through some documents in the portal and ended up with lots of confusion. Could some one help with the procedure to update the user password. (We need to change the passwords for existing projects as well.)

PS: We are using ALM 12.20 in Linux environment. 

please respond at the earliest.

Thanks & regards

sailaja Ch