The system should alert you if an issue causes the data to not be persisted, but if you'd like to explicitly confirm there are a couple of different options that I can think of offhand (beyond using external DB tools to directly query the database).
You can use a report definition to retrieve one or more of the type of objects you are saving in your activity:
If you create a report definition in the class for which you want to check the value of the property then you will not have to explicitely mention the table name or any join.
For example your class structure is ABC-XYZ-work-CaseType1 where CaseType1 is your Case Type. Now if you have prop1 and prop2 2 properties created in CaseType1 and you want to check the values of these 2 properties of the work object then create a Report definition in this class (ABC-XYZ-work-CaseType1). Mention the two property names in the query tab, save the report and run the report.
When you create RD in class ABC-XYZ-Work-Casetype1 and mention the property of the this class in RD by default the table mapped to this class gets mapped to this RD. You don't have to explicitly map the DB table.
after executing "run" , the end of the case, I can check data in pyWorkPage of clipboard, but I cannot find it in any database and data page" D_xxx". How can I see the content in database? I created report definition to check data in database, but nothing seems to come...
Have you configured a Data Page? You will see the result in the Data Page only if you have a configured a Data Page sourced with the report definition.
Also what do you mean by "I cannot find it in any database" ? Where exactly are you checking the values in the DB? Are the properties that you are checking exposed? If the properties are not exposed you will not be able to see the data as they will be stored in BLOB (pzpvstream).