An image forming system, comprising: an image forming apparatus comprising: a communication interface to receive print data; an image former to perform a print job using the received print data; a controller to generate first job log data comprising one or more accumulated amounts of sheets used at the time of a print job and second job log data comprising amounts of sheets used in respective print jobs, when the print jobs are completed, and to generate third job log data by processing the second job log data to include the one or more accumulated amounts of sheets of the first job log data; and a storage device to store the first job log data and the third job log data; and a printing control terminal, comprising: a communication interface arranged to receive the third job log data from the image forming apparatus, and a controller configured to determine whether first or second job log data have been lost by determining the difference between accumulated amounts of sheets for two consecutive print jobs in the third job log data and comparing the result with the number of sheets used in the more recent of the two consecutive print jobs using the third job log data, and if the comparison indicates a difference between the compared values, to identify that first or second job data have been lost and to request the lost job log data from the image forming apparatus. an image forming apparatus comprising: a communication interface to receive print data; an image former to perform a print job using the received print data; a controller to generate first job log data comprising one or more accumulated amounts of sheets used at the time of a print job and second job log data comprising amounts of sheets used in respective print jobs, when the print jobs are completed, and to generate third job log data by processing the second job log data to include the one or more accumulated amounts of sheets of the first job log data; and a storage device to store the first job log data and the third job log data; and a communication interface to receive print data; an image former to perform a print job using the received print data; a controller to generate first job log data comprising one or more accumulated amounts of sheets used at the time of a print job and second job log data comprising amounts of sheets used in respective print jobs, when the print jobs are completed, and to generate third job log data by processing the second job log data to include the one or more accumulated amounts of sheets of the first job log data; and a storage device to store the first job log data and the third job log data; and a printing control terminal, comprising: a communication interface arranged to receive the third job log data from the image forming apparatus, and a controller configured to determine whether first or second job log data have been lost by determining the difference between accumulated amounts of sheets for two consecutive print jobs in the third job log data and comparing the result with the number of sheets used in the more recent of the two consecutive print jobs using the third job log data, and if the comparison indicates a difference between the compared values, to identify that first or second job data have been lost and to request the lost job log data from the image forming apparatus. a communication interface arranged to receive the third job log data from the image forming apparatus, and a controller configured to determine whether first or second job log data have been lost by determining the difference between accumulated amounts of sheets for two consecutive print jobs in the third job log data and comparing the result with the number of sheets used in the more recent of the two consecutive print jobs using the third job log data, and if the comparison indicates a difference between the compared values, to identify that first or second job data have been lost and to request the lost job log data from the image forming apparatus.