- The next available value stored in DBC.IdCol.AvailValue
- The defined incremental identity column batch size for the system
This quantity is specified by the DBS Control parameter IdCol batch size. For more information, see Teradata Vantage™ - Database Utilities, B035-1102 and Optimizing Bulk Inserts Into an Identity Column.
When the pool of available identity column numbers in the cache is exhausted, Vantage must update DBC.IdCol.AvailValue and obtain a new range of numbers.
If an ongoing transaction has DBC.IdCol locked, as it would during a SELECT statement against the table, then system access to the column number pool is temporarily blocked and all inserts into the relevant identity column table are suspended until the transaction either commits or aborts. A SELECT statement against DBC.IdCol places an ACCESS lock on the table.
The SELECT privilege on DBC.IdCol is restricted to user DBC and any user explicitly granted the privilege by DBC.
- The SELECT statement is run within the boundaries of an explicit transaction.
- Concurrent INSERT operations are being performed on an identity column table.