| Product: | DBConnectivity Products for IBM Db2 for i (HiT ODBC/400, HiT OLEDB/400, Ritmo/i, HiT JDBC/400) |
| Version: | All |
| ID: | 1061 |
| Summary: | The QZDASOINIT job sometimes uses up all the processing power on the IBM i. This can be caused by the Querry Optimizer not being able to find table indexes |
The QZDASOINIT job sometimes uses up all the processing power on the IBM i. This can occur when accessing tables that do not have indexes.
The Query Optimizer program running on the IBM i decides how to execute a query and cannot be adjusted in anyway. When you make a select on a table, the optimizer decides which indexes or logical views to use in order to get the best performance. The problem is that sometimes the indexes are not recognized by SQL Query Optimizer and are not used. Therefore, using logical files with the SQL language does not necessarily imply using the indexes specified by the logical file. The SQL Query Optimizer decides which indexes to use and, if there are none available, builds them on the fly.
Whether logical files can be accessed or not depends on how they were created. If ODBS recognizes the logical files, the driver can access them. Otherwise they cannot be accessed.