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M&M FDT 1.2.1 Online Specification |
Interfaces and Methods - Schemas - FDT Specification - Quicklinks - Abbreviations
4.9.8.2 IFdtContainer::LockDataSet()
| This method can be called in the states: |       |
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HRESULT LockDataSet ( [in] BSTR systemTag, [out, retval] VARIANT_BOOL* result ); |
Description:
| A DTM sends an notification to the Frame Application that it wants to have exclusive write access for the currently loaded data set. |
Parameters:
| systemTag | Identifier of the device instance |
Return Value:
| result | TRUE Data set is locked for write access FALSE Data set could not be locked. DTM has read access only |
Behavior:
| Via this method a DTM notifies the database that it wants to modify or delete the specified instance data set. It is up to the Frame Application to validate this request within a multi-user multi-session system. If the request fails, the DTM must not change any data and should set all input fields to ‘non edit’ in case of an open user interface. It is in the responsibility of the Frame Application to reject write-requests if a DTM does not take care about its read only status. A DTM must not lock it’s instance data for the complete lifetime. Instead the DTM should try to lock data only if instance data is going to be modified and should unlock the data after the instance data is saved and no further modifications are expected. |
Comments:
| Within a single user system the method returns always TRUE. Examples for lock conditions are: - a user interface is active, that allows changing the instance data - the DTM received the request to change data via its COM-interfaces (IDtmParameter, IDtmSingleInstanceDataAccess) |
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Last updated 2015-02-05 15:17
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