A context is a mapping between logical and physical schemas.
So, in context DEV, logical schema LS is mapped to physical schemas PS1 which is setup to use Oracle schema ORA1.
In context TEST, the same logical schema LS is mapped to physical schemas PS2 which is setup to use Oracle schema ORA2.
Hence, on different contexts, different Oracle schemas (for example) will be read.
So you need to check for a context and a logical schema, if the correct physical schema is used.
Thanks Adrian. I used another alternate, I have created new setup (Physical/logical arch & context) for this requirement and now I can point to required source systems just by changing the context.