The values used for data dictionary content in any particular connection on a Heterogeneous Services database link can come from any of the following sources, in order of precedence:
Instance information uploaded by the connected Heterogeneous Services agent at the start of the session. This information overrides corresponding content in the Oracle data dictionary, but is never stored into the Oracle data dictionary.
Instance information stored in the Oracle data dictionary. This data overrides any corresponding content for the connected class.
Class information stored in the Oracle data dictionary.
If the Oracle database server runs with the HS_AUTOREGISTER server initialization parameter set to FALSE, then information is not stored automatically in the Oracle data dictionary. The equivalent data is uploaded by the Heterogeneous Services agent on a connection-specific basis each time a connection is made, with any instance-specific information taking precedence over class information.
Note:
It is not possible to determine positively what capabilities and what data dictionary translations are in use for a given session due to the possibility that an agent can upload instance information.
You can determine the values of Heterogeneous Services initialization parameters by querying the VALUE column of the V$HS_PARAMETER view. Note that the VALUE column of V$HS_PARAMETER truncates the actual initialization parameter value from a maximum of 255 characters to a maximum of 64 characters. It truncates the parameter name from a maximum of 64 characters to a maximum of 30 characters.