Why are RDBMS'es CS systems in the CAP sense according to this graphic?


According to the picture: 1. Why is Mongodb,...(CP) 2. Why is CouchDB,..(AP) 3. Why is Rdbms (CA)

Note: Why does partition tolerance not matter for an RDBMS?

enter image description here

Answer

An RDBMS doesn't have to be in the CA region because all that the name says is "it's relational". It could be anywhere. But most RDBMS'es are. Let's assume they are.

They are on a single node which means there are no partitions to worry about. Partitions are between nodes.

If you consider the system RDBMS+clients it's a multi-node system and being CA then means in case of a partition you will loose one of CA, possibly both.

source: stackoverflow.com
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