> ## Documentation Index > Fetch the complete documentation index at: https://docs.zeotap.com/llms.txt > Use this file to discover all available pages before exploring further. # Reserved Catalogue Fields > Reserved fields are already part of your organisation’s catalogue. These fields are reserved for system use. Therefore, a field with the same name cannot be recreated for any other purpose. | **RESERVED FIELD NAME** | **DISPLAY NAME** | **DESCRIPTION** | | :---------------------- | :----------------- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | \_\_version | \_\_version | This field is internal to Zeotap. | | ucid | Unique Customer ID | Unique Customer ID is an identifier created per uniquely identified user.
It is tied to all other identifiers across all sources of data onboarded and ingested to Zeotap. | | datasetname | Source Name | This field holds the name of the source created in Zeotap. | | datasetId | Source | This field holds the Unique ID assigned to a source created in . | | datasourceId | Source Type | This field holds the Unique ID assigned to the different data source ID in Zeotap. | | datagroupId | Collection ID | This field is internal to Zeotap. | | orgId | orgId | Unique Identification number assigned to an organisation. | | linked\_ucid | Linked Ucid | This field is internal to Zeotap. | | datagroup | Collection Name | This field is internal to Zeotap. | | \_zeotap\_filepath | \_zeotap\_filepath | This field is internal to Zeotap. | | \_zeotap\_ts | \_zeotap\_ts | Timestamp of data ingestion |