@cbauernf
Let me introduce this new feature to you.
WFA4.0 has introduced 'scheme management' which allows you to create a new scheme. WFA3.1 and earlier didn't allow you to create a scheme, but the new scheme only gets created via dictionary.
When you create a new scheme, you need to select a 'Type' for it

1. Data source Acquistion : The scheme will be used for Data Source Acuquistion. This means that only WFA can fill data in this scheme using WFA Data Source acquistion methods i.e. SQL or Script. The default WFA DB user 'wfa' will not be able to write data into this scheme. Only WFA can fill data via acquisition mechanisms.
2. Other : This scheme is for purpose other than Data Source acquistion. This sheme will NOT appear to you in the drop-down selection for a new Data Source type. The default DB user 'wfa' has full priviledges on this scheme. So I can fill data in this scheme using INSERT query statements.
The playground as in 3.1 was the only scheme where DB user 'wfa' could fill data directly. In WFA 4.0 definition, this fall for the 'Other' scheme. Hence you are not being shown the play ground scheme for creating a new Data Source Type.
I would want to know what is the purpose of choosing the 'playground' scheme for your data Source script?
What can you do if you still want to use playground itself?
I can provide you some ways and that may depend on the answer to the above question.
sinhaa
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