Precautions - Mitsubishi Electric MELSEC iQ-R-R00CPU User Manual

Precautions

This section describes the precautions for using the CPU module database access function.
Database creation
When creating a database in the CPUDB folder, use characters that can be specified only. If the characters that cannot be
specified are used to create the database, the table cannot be accessed by the database access instructions.
For the characters that can be specified, refer to the following.
Page 237 Setting details of Unicode text file
Combination of the firmware version and database
The following table lists the combination of the firmware version of the programmable controller CPU that creates the
database and that of the programmable controller CPU where the operation of the database is available.
: Available, : Not available
Database
Database created with the programmable controller CPU with firmware
version earlier than "28"
Database created with the programmable controller CPU with firmware
version "28" or later
*1 If the database that has been operated with the programmable controller CPU with firmware version "28" or later is operated with the
programmable controller CPU with firmware version earlier than "28", the operation is completed with an error.
Number of connections that can be operated simultaneously
Up to four connections can be operated with the CPU module database access function simultaneously.
However, if an application such as Microsoft Access uses several connections, four applications may not connect with the
database of the CPU module simultaneously. If an attempt was made to connect with the database with all the connections
used, an error occurs in the application and the database cannot be connected. In this case, end unused applications
connected with the database and connect again.
Several simultaneous accesses
When several applications access the same database in the CPU module, the database processing becomes slow.
■Access to the same table
When the database access instructions or the CPU module database access function access the same table, the function
executed first locks the table, and an error may occur in the function executed later. For the database access instruction, an
error code is stored in the completion status.
■Definition change of the same database
When the database definition is changed with "CREATE TABLE" or "DROP TABLE" in a single database from several
applications using the CPU module database access function, the application executed first locks the database and an error
may occur in the function executed later.
Availability
The programmable controller
CPU with firmware version
earlier than "28"


13.3 CPU Module Database Access (from External Device) Function
The programmable controller
CPU with firmware version
"28" or later
*1


13 DATABASE FUNCTION
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