In order to catalog a tcp/ip node, I need to specify a port number. I believe that the port number is the number used at the time of creating the instance.
what I would like to know is what exactly is the concept of a port number ?
how do you decide on what is your port number ? or how do you decide on which is the next port number one should use for a new instance ? can the port number be changed after the instance is created ? if yes, how ?
is there a default port number that's used in case we do not specify a port number ?
Yes, the port number you specified when creating theinstance is the value you use when configuring the client to communicate to the instance.
To understand port numbers, think of you Server as a building with lots of departments. The address of the the building is its IP address. Each department has a door that when someone wants to use the service of that department, they need to come to the correct door to get proper service. The port number is like the door. You want to make sure that DB2 is servicing you database requests and not some other service on the server like the print server.
To decide what port number to use depends on your network security configuration. Yes, the port number can be changed after creation, but it is not easy and how to do it varies depending on the OS of the server.
There is no default value when setting up the client, it must be specified.