In Teradata 15 doc I read that "BYNET maintain HASHMAP", this means Hashmap stored in BYNET and when PE send rowhash then BYNET identify the AMP based on Hashmap entries available with it. Please correct me if I am wrong. If Hashmap not present in BYNET, then where it exist?
Hashmaps are so-called globally distributed objects (gdo), i.e. flat files stored on each node (in /etc/opt/teradata/tdconfig) and loaded into memory during startup.
Reading the hashmap.gdo into RAM is part of the PDE startup.
I don't know if/where the startup procedure is explained in detail, but the Support Utilities manual has some topics, e.g.