code: private void validateBackupConfig(RepositoryBackupConfig config) throws BackupConfigurationException
     {
        if (config.getIncrementalJobPeriod() < 0)
        {
           throw new BackupConfigurationException("The parameter 'incremental job period' can not be negative.");
        }
  
        if (config.getIncrementalJobNumber() < 0)
        {
           throw new BackupConfigurationException("The parameter 'incremental job number' can not be negative.");
        }
  
        if (config.getIncrementalJobPeriod() == 0 && config.getBackupType() == BackupManager.FULL_AND_INCREMENTAL)
        {
           config.setIncrementalJobPeriod(defaultIncrementalJobPeriod);
        }
     }
docs: Initialize backup chain to workspace backup.
  
  @param config
  @return
  @throws BackupOperationException
  @throws BackupConfigurationException
  @throws RepositoryException
  @throws RepositoryConfigurationException