Before validating an external partitioned table you need to create the external partitioned table. To create an external partitioned table use the procedure DBMS_CLOUD.CREATE_EXTERNAL_PART_TABLE (see Query External Partitioned Data (with Partitioning Clause) for more details):

BEGIN
  DBMS_CLOUD.VALIDATE_EXTERNAL_PART_TABLE (
    table_name => 'PET1',
    partition_name => 'P1');
END;
/

This procedure scans your source files for partition P1 and validates them using the format options specified when you create the external partitioned table.

The validation of a partitioned table by default validates all the partitions sequentially until rowcount is reached. If you specify a partition_name then only a specific partition is validated.

The validate operation, by default, scans all the rows in your source files and stops when a row is rejected. If you want to validate only a subset of the rows, use the rowcount parameter. When the rowcount parameter is set the validate operation scans rows and stops either when a row is rejected or when the specified rowcount number of rows are validated without errors.

For example, the following validate operation scans 100 rows and stops when a row is rejected or when 100 rows are validated without errors:

BEGIN 
  DBMS_CLOUD.VALIDATE_EXTERNAL_PART_TABLE (
     table_name => 'PET1',
     rowcount => 100 ); 
END; 
/

If you do not want the validate to stop when a row is rejected and you want to see all rejected rows, set the stop_on_error parameter to FALSE. In this case DBMS_CLOUD.VALIDATE_EXTERNAL_PART_TABLE scans all rows and reports all rejected rows.

If you want to validate only a subset of rows use the rowcount parameter. When rowcount is set and stop_on_error is set to FALSE, the validate operation scans rows and stops either when the specified number of rows are rejected or when the specified number of rows are validated without errors. For example, the following example scans 100 rows and stops when 100 rows are rejected or when 100 rows are validated without errors:

BEGIN
  DBMS_CLOUD.VALIDATE_EXTERNAL_PART_TABLE (
     table_name => 'PET1',
     rowcount => 100 
     stop_on_error => FALSE );
END; 
/

See VALIDATE_EXTERNAL_PART_TABLE Procedure for more information on DBMS_CLOUD.VALIDATE_EXTERNAL_PART_TABLE.

See View Logs for Data Validation to see the results of validate operations in the tables dba_load_operations and user_load_operations.