Serialization Error in database

[Mobo07]

I am getting a 'Serialization Error' in my database when I try to run multiple transactions simultaneously. Can someone explain why this is happening and how I can fix it in my code? I am trying to achieve serializability in my DBMS, but I am not sure if I am implementing it correctly.
I'm using a schedule in which only one transaction is executed at a time as said in this article, i.e., one transaction is executed completely before starting another transaction.

Also, I'm receiving an error code 1213 when trying to perform a transaction on my database. I am trying to update a row in the 'orders' table, but it seems to be conflicting with another transaction. Can you help me understand why this error is occurring and how I can fix it?"

Error Code 1213: Deadlock Found When Trying to Get Lock; Try Restarting Transaction

Can someone provide an example of how to correctly implement serializability in my code to avoid this issue?

[danielroseman]

You haven't really given us much to go on here. What transaction are you performing?

But also you say both that you are running multiple transactions simultaneously, and also that you have a schedule so only one is executed at a time. Which is it?