Thank you Philip for your contribution
.
As illustrated by Phil, the TLServer File Service function is wonderful if the PLC can be connected to a PLC via RS232 or RS485 and you can practically store unlimited amount of data to a PC harddisk.
However, if the PLC is standalone, you still can use the built-in EEPROM to store whatever data. There are 1700 words of EEPROM data memory which can be accessed via an Index. So you can store multiple sets of data by referencing the position of an index pointer. Once you fill up a certain block of data EEPROM you can move the index pointer back to the first EEPROM position and overwrite the old data there - sort of implementing a circular buffer for the data.
The EEPROM can be overwritten up to 100,000 times which should be quite sufficient for most applications. The key to using the EEPROM is not to keep writing to the EEPROM. So you should only use the differentiated custom function to execute the SAVE_EEP function to store data to the EEPROM.