There are two lock levels in Teradata:
table: sessions block each other
hash: sessions can do transactions simultaniously unless they try to access the same RowHash (e.g. use the same PI values) or need a table level lock.
INSERT VALUES locks on a RowHash level.
An Insert/Select will be blocked, a Delete/Update specifying the PI will succed.
When you don't see a locking step in Explain it's a hash lock.
Dieter
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