The DMF must include a process to identify and select relevant data sources within the institution for each type of data and model. If an institution recently merged or acquired another entity, it must carry out the necessary steps to retrieve historical data from these entities.
5.2.2
If internal sources are lacking in data quality or quantity, institutions may rely on external sources. However, if an institution decides to rely on external data for modelling, it must demonstrate that the data is relevant and suitably representative of its risk profile and its business model. External data sources must be subject to an identification and selection process. The DMF governance and quality control also apply to external data employed for modelling.
5.2.3
Once a source has been selected, institutions are expected to retain this source long enough to build consistent time series. Any change of data source for the construction of a given data set must be rigorously documented.