7 APPLICATION INSTRUCTIONS
7.21 Database Access Instructions
981
7
• These instructions declare the start of a transaction in relation to the database corresponding to the identification number
specified by (s). However, if a data base other than the one specified by (s) is open, the DBTRANS instruction cannot start
a transaction and is completed with an error.
• Upon normal completion, the completion signal in the completion device (d1) is turned on and 0 is stored as the completion
status in the device (d2).
• The following figure shows the operation of the completion device at completion of the DBTRANS(P) instruction.
• After a transaction is started by the DBTRANS(P) instruction, the DBCOMMIT(P) instruction needs to be executed to
determine the transaction or the DBROLBAK(P) instruction needs to be executed to restore the state before the start of the
transaction. (If the DBCLOSE(P) instruction is executed before DBCOMMIT(P) or DBROLBAK(P), the transaction is
determined in the status at the execution of the DBCLOSE(P) instruction.)
• SM753 (File being accessed) turns on while the DBTRANS(P) instruction is executed.
*1
While SM753 is on, the
DBTRANS(P) instruction cannot be executed. If executed, no processing is performed. However, the instruction has been
completed with an error while the database access instruction is being executed.
• When "To Use or Not to Use the Built-in Database Access" is set to "Use" in the module parameter of the CPU module, the
DBTRANS(P) instruction cannot be executed while SM1498 (CPU module database start-up flag) is off.
*1
If executed, no
processing is performed.
*1 For the firmware versions supporting SM753 and SM1498, refer to the list of special relay areas. ( MELSEC iQ-R CPU Module
User's Manual (Application))
In the following cases, the error completion signal in (d1)+1 is turned on and an error code is stored as the completion status
in the device (d2).
• The DBTRANS(P) instruction is executed during execution of the database access instruction.
• An identification number outside the range is specified.
• The DBTRANS(P) instruction is executed while the transaction has already been started.
• A data base other than the one specified by (s) is open.
• The identification number of a database which is not open is specified by (s).
For the error code stored in the completion status of the operand, refer to the following.
Page 986 Error codes related to database access instructions
Error code
(SD0)
Description
2820H The area specified by (d1) exceeds the applicable range of the device/label used.
OFF
OFF
ON
ON
Program
DBTRANS(P) instruction
END processing END processing
Starting the
transaction
Completion device (d1)
Completion device (d1)+1
END processing
Error completion
To Next Page
Loading...
