After objects are mapped for comparison and synchronization, you may encounter warnings on the Mapping page of the Data Comparison wizard. The warnings may be divided into two groups. They are table-level warnings and column level warnings.
Table-level warnings are displayed as icon in the column with check boxes on the Mapping page of the Data Comparison wizard. Object pairs with table-level warnings are not compared. They are displayed with icon instead of check box in the Data Comparison document.
Column-level warnings are displayed as Caution icon in the Columns in Comparison column on the Mapping page of the Data Comparison wizard. They also appear in the Target column in the Column Mapping dialog box. Such warnings mean that some columns of a compared object pair cannot be compared because of type incompatibility or that you may encounter data loss when synchronizing data.
To read the warning messages, point to the warning icon. All warnings for this object will appear in the hint.
The following table contains information about table-level warnings and ways to remove them.
|No columns to compare.||It means, there are no columns with the same name in this pair of tables (views). To compare them you should map the columns manually. For more information about the column mapping, see Mapping Columns.|
|Objects to compare have no key column.||It means that custom comparison key is used but is not set. You should mark at least one column pair as comparison key. For more information visit Setting Comparison Key.|
The following table contains information about column-level warnings.
|Conversion is possible, but may fail in case of incompatible data.||Conversion between columns ColumnName1 and ColumnName2 is possible, but may fail in case of incompatible data.|
|Columns have different precisions.||Columns ColumnName1 and ColumnName2 have different precisions, data migration may cause overflows.|
|Date or time columns have different data format.||Date and time columns ColumnName1 and ColumnName2 have different data format, migrating the data may cause truncation.|
|Numeric columns have different precisions.||Numeric columns ColumnName1 and ColumnName2 have different precisions, migrating the data may cause rounding.|
|Columns have different sizes.||Columns ColumnName1 and ColumnName2 have different sizes, migrating the data may cause truncation.|
|Source column allows Nulls which can not be stored in target.||Source column ColumnName1 allows Nulls which can not be stored in target column ColumnName2, data migration may cause error.|
|RowID columns have different formats.||RowID columns ColumnName1 and ColumnName2 have different formats.|
|Data type is not supported.||Data type ColumnName1 of the ColumnName2 column is not supported.
For the Direct mode: Data type ColumnName1 of the ColumnName2 column is not supported in the direct mode.
|CLOB data could be spoiled.||Columns ColumnName1 and ColumnName2 have CLOB or NCLOB data types. Oracle 8 does not support textual encoding for loading CLOBs and NCLOBs from files, hence if you have non-latin characters data of these data types, you may lose it. Please turn off the Synchronize LOBs via files option, or use it at your own risk.|
|Types are incompatible.||These columns cannot be compared. This warning appears when data of the source column cannot be converted to the data type of the target column, for example, RAW and NUMBER.|
You may exclude columns from comparison and synchronization either by unmapping them or by clearing the check boxes in the first column of the Select columns for comparison grid on the Column Mapping dialog box.