Permanence of data is not one advantage of secondary data.

For all secondary data sets coverage will be concerned with ensuring that sufficient data remain for analyses to be undertaken once unwanted data have been excluded.

Validity of big data is whether the data are correct.

Aggregations and definitions may be unsuitable is one disadvantages of secondary data.

Access may be difficult or costly is one disadvantages of secondary data.

Secondary data is data which can be collected specifically for the purpose of answering a research question(s) and to meet research objectives.

Many large organisations also undertake regular surveys.

Reanalysing secondary data can also lead to unforeseen or unexpected new discoveries and new insights.

Continuous or regular survey secondary data will have been collected through census a distinct subtype of survey strategy.

Big data comprise predominantly unstructured data.