System Checks and Messages During Data Entry 
System Checks and Messages During Data Entry
Use
CATS classic
aims to make data entry as easy as possible. This includes validity checks, which the SAP System runs on all the data that you enter. If you have entered an order number that does not exist, for example, the system issues a message to bring this to your attention. You can then correct the data.The messages appear either in a dialog box or at the foot of the screen.
See also:
Features
Depending on the type of data, the checks are made when you:
Save data
Data entry view, 
Release view, 
Variable view).
An exception is when you exit the release view. The system does not check for errors in this case, since the user is not able to correct any errors that occur at this point.
Released records undergo more thorough checks than records assigned the
In the standard system, validity checks are carried out when you perform any of the above activities.
In addition, you can define the following checks in the system:
Profile-dependent checks
You can define the following checks for entered hours or clock times when you maintain your data entry profiles:
This check prevents a user from being able to enter more than 24 working hours for one day.
If you enter data on external services, you can assign several persons one personnel number. If this case, you should not specify the 24 hours check.
The 24 hours check is carried out when you perform any of the above actions for records assigned the processing statuses In process and Released.
This switch is only relevant for data records that specify clock times. It checks for and prevents overlaps between the clock times you enter.
If you implement HR, the system checks that no more data is entered for a day once a full-day absence has been entered.
The system checks for collisions in the data entry period currently being processed when you perform any of the above actions. The processing status assigned to the data is irrelevant in this case.
Profile-dependent checks for users of HR Time Management (PT)
If you implement HR Time Management, you can also validate the data against target hours and quotas, and check for collisions between attendances and absences.
See also:
Customer-defined checks
The SAP enhancements CATS0003 (Validate recorded data) and CATS0006 (Validate entire time sheet) allow you to extend the standard checks by defining your own checks.