|xid||Transaction start id. Marks the logical beginning of the transaction.|
|iid||Invocation id. Marks the beginning of a statement within a transaction.|
Commit id. Marks the id at which transaction changes are visible to other transactions.
The following table describes MVCC visibility rules in different isolation levels. Note that ClustrixDB does not support the read uncommitted level.
ClustrixDB implements row level locks for transactions which touch a few rows at a time (a runtime configurable variable). For statements which affect a signification significant portion of a table, the query optimizer will promote row level locks to a table lock.