code: public Observable<BackupShortTermRetentionPolicyInner> beginCreateOrUpdateAsync(String resourceGroupName, String serverName, String databaseName, Integer retentionDays) {
          return beginCreateOrUpdateWithServiceResponseAsync(resourceGroupName, serverName, databaseName, retentionDays).map(new Func1<ServiceResponse<BackupShortTermRetentionPolicyInner>, BackupShortTermRetentionPolicyInner>() {
              @Override
              public BackupShortTermRetentionPolicyInner call(ServiceResponse<BackupShortTermRetentionPolicyInner> response) {
                  return response.body();
              }
          });
      }
docs: Updates a database's short term retention policy.
  
  @param resourceGroupName The name of the resource group that contains the resource. You can obtain this value from the Azure Resource Manager API or the portal.
  @param serverName The name of the server.
  @param databaseName The name of the database.
  @param retentionDays The backup retention period in days. This is how many days Point-in-Time Restore will be supported.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the BackupShortTermRetentionPolicyInner object