Appendix B
B-11
B
NJ/NX-series Database Connection CPU Units User’s Manual (W527)
B-2 Execution Time of DB Connection Instructions
B-2-1 Restrictions to Execution Time of DB
Connection Instructions
B-2 Execution Time of DB Connection Instructions
This section describes execution time of DB Connection Instructions.
B-2-1 Restrictions to Execution Time of DB Connection Instructions
Execution time of DB Connection Instructions varies according to the following factors.
Status of the NJ/NX-series CPU Unit
DB type
Processing capability and load status of the server that contains the DB
DB response time
Contents of the SQL statement to execute
Number of retrieved records in the execution of DB_Select instruction
Due to the above factors, execution time of a DB Connection Instruction may exceed the reference
value given in B-1-2 Reference Values for Execution Time of DB Connection Instructions.
The following table lists the phenomena that we confirmed under our measurement environment and
their countermeasures.
1 After the power supply to the CPU Unit was turned ON, execution time of the first DB Connection Instruction (i.e.
DB_Insert, DB_Update, DB_Select, or DB_Delete instruction) got longer.
After execution of a DB_CreateMapping instruction, execution time of the first DB_Insert instruction got longer.
3 When communications or SD Memory Card processing was executed in the CPU Unit, execution time of a DB
Connection Instruction got longer.
Execution time of DB Connection Instructions is steadily long.
5 Depending on the DB’s status, execution time of a DB Connection Instruction (i.e., DB_Insert, DB_Update,
DB_Select, or DB_Delete instruction) got longer.
Refer to B-1-2 Reference Values for Execution Time of DB Connection Instructions for the
measurement conditions and items.
Phenomenon 1: After the Power Supply to the CPU Unit was Turned ON, Execution
Time of the First DB Connection Instruction (i.e. DB_Insert, DB_Update, DB_Select, or
DB_Delete instruction) Got Longer
Possible causes
The following can be the causes:
1. For the first DB Connection Instruction (i.e. DB_Insert, DB_Update, DB_Select, or DB_Delete
instruction) that is executed after the power supply to the CPU Unit is turned ON, the CPU Unit may
require longer processing time than usual.
2. For the first DB_Insert instruction that is executed after execution of a DB_CreateMapping
instruction, the DB may require longer processing time than usual.
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