Troubleshooting queries in Data Virtualization

Use these solutions to resolve problems that you might encounter with queries in Data Virtualization.

SQL messages in Data Virtualization
You can use the SQL message information to identify a problem and to resolve the problem by taking appropriate action.
Queries on virtualized flat files fail with incorrect results in Data Virtualization
When you virtualize flat files that are accessed by using a remote agent, some queries have incorrect results in cases where column type conversions are made for columns that have special characters.
SQL20478 error when you run a query
If a data masking rule applies to TableA and you run a query that uses CREATE TABLE ... AS SELECT ... FROM TableA, you might see an error message with Reason code "30". SQLCODE=-20478, SQLSTATE=428HD.
SQL0727N error when you query view results in Data Virtualization
You might encounter SQL0727N errors if you work in an environment that is heavily reliant on access control that is based on user groups.
SQL1822N error when you run a query in Data Virtualization
When you try to run a query, you get an error with code SQL1822N.
Concurrent queries are slow or fail in Data Virtualization
Data Virtualization does connection pooling and when connection pools become full, performance can be negatively impacted.
Incorrect query results for Db2 remote data sources in Data Virtualization
If you run queries that compare string data types against Db2® remote databases, which use the Db2 connection type that is not in VARCHAR2 compatibility mode, these queries might return incorrect results.
Data type STRING in Hive tables is assigned CLOB data type in Data Virtualization
When you virtualize tables in a Hive data source, Data Virtualization converts data with type STRING to type CLOB instead of type Varchar when it exceeds the maximum string length.
Data types STRING, TEXT, and VARCHAR in Snowflake tables are assigned CLOB data type in Data Virtualization
When you virtualize tables in a Snowflake data source, Data Virtualization converts data with types STRING, TEXT, and VARCHAR to type CLOB instead of type VARCHAR when they exceed the maximum string length.
Performance issues in queries with subqueries in Data Virtualization
If you run a query that has subqueries, you might encounter performance issues.
SUM() or AVG() function returns an error in Data Virtualization
You might encounter an SQL0802N error when you use the SUM() or AVG() function in certain SQL statements.
Table statistics are not collected in Data Virtualization
When you create virtual tables, some of the table statistics are not collected correctly.

Parent topic: Troubleshooting the Data Virtualization service