Mitsubishi Electric MELSEC Q Series User Manual page 337

(2) Precautions for file operations
This section describes the operations and precautions of memories and drives of the C Controller module.
(a) File writing
Before writing files by FTP and Telnet, etc. during user program operations, make sure that the file(s) to write
will not affect the running user program.
(b) File writing destination
Do not write files to the standard ROM with a user program.
Since a standard ROM has a write cycle limit, the life of C Controller module will be shortened.
When writing files using a user program frequently, write to a standard RAM, CompactFlash card, or network
*1
device (via FTP/NFS/netDrv).
*1 : For details, refer to the manual for VxWorks.
(c) Access to the same file
Files being written are not accessible.
Files being accessed are not writable.
(d) Operations not allowed during file access
Do not operate the following operations during file accessing to the standard ROM, standard RAM, or
CompactFlash card. Doing so may result in data corruption or file system error in the CompactFlash card.
• Power OFF
• Reset
• Unmount of a CompactFlash card
• Removal of a CompactFlash card
Configure the program to close the file(s) being accessed and perform the above operations when you access
user file(s) in any of the above memories.
(e) The number of files and directories
The maximum number of files and directories that can be created in the root directory of the following
memories are 256.
• Standard ROM
• Standard RAM
• CompactFlash card
However, the maximum number may be reduced depending on file name length and character types.
Moreover, the number directories and the number of files in the root directory are 100 or less. Set this number
to 500 or less.
If you store more files or directories than the above-mentioned, the file access time might significantly increase.
Due to this, it may affect the operation of the C controller module and user program.
(f) Creating a directory
Do not create a directory in the root "/" of the C Controller module. Such directory creation processing fails or
an unintended directory may be created. (These errors occur also when transferring a directory to the root "/"
through FTP.)
CHAPTER 18 MEMORIES AND FILES
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