About synchronizing schemas

Synchronizing schemas is the process of updating the metadata of a registered data source in Collibra Data Intelligence Platform.

You can synchronize a schema manually or automatically at fixed intervals:

• Synchronize manually if you want to test the synchronization of your data source or if you want to synchronize immediately.
• Synchronize automatically if the content of the data source changes regularly.

Synchronization process

• After you have registered a data source via Edge, Data Catalog connects to your Edge site to create a list of schemas from the registered database.
  You can see the schema list on the Configuration tab page of the Database asset page.
• You can refresh the schema list in the Configuration tab page, by clicking the Refresh List icon.
• You can synchronize all schemas that have one or more synchronization rules.
• During the synchronization process, the Edge site connects to your data source again and ingests all schemas, tables and columns according to the synchronization rules. Collibra Data Intelligence Platform also detects whether there are changes since the last synchronization of a schema. Edge resolves the possible conflicts in the following way.

  Tip Before starting the synchronization, we recommend to click the Refresh List icon to get the latest schema information from the data source.

  Change in data source	Result in Collibra	Required action
  A table, column or foreign key has been added to the schema.	Collibra creates the assets.	No action is required of you.
  A table, column or foreign key has been removed from the schema.	The existing asset receives the Missing from source status. If it concerns a table, also the related Column assets receive the Missing from source status. This process is called soft delete.	If needed, you can manually delete the assets.
  A schema is empty.	We don't synchronize the schema. Nothing changes in Collibra.	If needed, you can manually delete the assets.
  A schema has been removed.	The schema receives the Missing from source status. Also the related Table and Column assets receive the Missing from source status. This process is called soft delete.	If needed, you can manually delete the Schema asset and all related assets.
  A column or foreign key has been renamed.	Collibra creates an asset with the new name. The existing asset receives the Missing from source status. This process is called soft delete.	If needed, you can apply any manual changes you made to the original asset, to the new asset. And then remove the assets that are no longer applicable.
  A table has been renamed.	Collibra creates a Table asset with the new name. Collibra also creates new Column assets for the new Table asset. The existing Table and related Column assets receive the Missing from source status. This process is called soft delete.	If needed, you can apply any manual changes you made to the original assets, to the new assets. And then remove the assets that are no longer applicable.
  A schema has been renamed.	Collibra creates a Schema asset with the new name. Collibra also creates new Table and Column assets for the new Schema asset. If you have refreshed the schema list before the synchronization, the existing schema and related assets receive the Missing from source status. This process is called soft delete.	If needed, you can apply any manual changes you made to the original assets, to the new assets. And then delete the assets that are no longer applicable.

  Any created assets receive a unique full name (fully qualifying name) based on Edge naming conventions.

  Schema, Table, Column or Foreign Key assets with the Missing from source status don't block the synchronization process.

  Note In the asset diagram, assets with the Missing from source status are shown by default. If you don't want to see these assets, apply a filter to the diagram view to only display assets with valid statuses.

  Important If you rename a database in the data source, the Edge synchronization process will consider it a new database. We don’t detect the renaming of a database at this moment.

• If, in the rule, you have indicated you want to include source tags, the tags defined on the assets in the data source are registered and available from the Schema, Table, Database View, and Column assets in the Source Tags attribute. For more information, go to Source tags.
• If a schema is synchronized, you see a check symbol () next to the schema name.
  If the synchronization of a schema fails or the schema is no longer available in the source, an exclamation mark () is shown instead.
  You can also see the synchronization status in the Activities list.

  

  

• After the synchronization, the synchronized data becomes available. To see which data is added, go to Metadata synchronization results.
• If you no longer want to synchronize a schema, and delete associated assets, go to Remove a synchronized schema.

Synchronization rules

The synchronization rule determines which tables of a schema you synchronize in Data Catalog.

• You can add up to five synchronization rules. The order of the rules is important. For all information, go to Configure the synchronization of a data source.
• The Schema asset and the Foreign Key assets are always ingested in the domain defined in the first rule.
• Only schemas that have at least one synchronization rule can be synchronized. If a schema has a synchronization rule, you see a table icon () next to the schema name.

The following table shows fields of synchronization rules:

Rule field	Description
Include Tables	A comma-separated list of the names of the tables you want to synchronize. In the list, add a space after each comma. For example, CUSTOMERS, ORDER, SKU. You can use * as a wildcard. For example, SKU*. The default value is *, which means all tables are taken into account. If the name of a table contains a special character, like . + * \ ? ^ $ ( ) [ ] { } | then add a \ before the special character for it to be correctly evaluated. For example, *SKU\+*. The Include Tables field is processed before the Exclude Tables field. Example  Out of all tables in a schema, you only want to synchronize the table with name "CUSTOMERS" and the tables with a name that starts with "ORDER". To do this: In the Include Tables field, enter: CUSTOMERS, ORDER*. Out of all tables in a schema, you only want to synchronize the tables with a name that contains "SKU". To do this: In the Include Tables field, enter: *SKU*. Out of all tables in a schema, you only want to include the tables with a name that contains "SKU+". To do this: In the Include Tables field, enter: *SKU\+*.
Exclude Tables	A comma-separated list of the names of the tables you do not want to synchronize. In the list, add a space after each comma. For example, CUSTOMERS, ORDER, SKU. You can use * as a wildcard. If the name of a table contains a special character, like . + * \ ? ^ $ ( ) [ ] { } | then add a \ before the special character for it to be correctly evaluated. For example, *SKU\+*. The Include Tables field is processed before the Exclude Tables field. You can use exclude to do the following: Synchronize all tables in a schema except the ones defined in the Exclude Tables field. Synchronize only tables as defined in the Include Tables field, with the exception of tables that are listed in the Exclude Tables field. Example  Out of all tables in a schema, you do not want to synchronize a table with the name "ADDRESS" and tables with a name that ends with "PHONE". To do this: In the Include Tables field, enter: * and in the Exclude Tables field, enter: ADDRESS, *PHONE. Out of all tables in a schema, you only want to exclude the table with name "example$table". To do this: In the Include Tables field, enter: * and in the Exclude Tables field, enter: example\$table. Out of all tables in a schema, you want to synchronize the tables with a name that starts with "SKU", but exclude the tables with a name that contains "bkp". To do this: In the Include Tables field, enter: SKU* and in the Exclude Tables field, enter: *bkp*. From the following list, only "SKU_1" and "SKU_2" will be synchronized. SKU_1 , SKU_2, SKU_bkp_1, SKU_bkp_2, New, bkp, bkp_SKU
Target Domain	The Physical Data Dictionary domain in which the schema is synchronized. The default value is Schema domain. The default value is Automatically Created for Schema. This means the metadata is placed in a domain located in the same community as the domain of your Database asset. If that domain doesn't exist yet, Data Catalog creates the domain using the following naming convention: [edge_connection_name] > [database_name] > [schema_name], for example Snowflake Connection > CERTIFICATION > CUSTOMERS. You can select any other Physical Data Dictionary domain for which you have a resource role with the Configure External System resource permission. It is advised, however, to have a domain per schema.
Options	Additional options to specify which type of tables you want to synchronize.
Exclude Database Views	A checkbox to exclude database views from the synchronization process. If selected, no assets of the type Database view are created. Tip You can also use Include Tables and Exclude Tables to include or exclude specific database views.
Include Source Tags	If you select this option, the tags defined on the assets in the data source are registered and available from the Schema, Table, Database View, and Column assets in the Source Tags attribute. Note Currently, you can synchronize source tags only from Snowflake.

Source tags

Tags created and assigned in the data source can be registered and synchronized in Data Catalog.
To do this, select the Include Source Tags checkbox when you define the synchronization rule for a schema. As a result, the tags defined on the assets in the data source are registered and available from the Schema, Table, Database View, and Column assets in the Source Tags attribute.

Note Currently, you can synchronize source tags only from Snowflake.

• The naming convention for source tags synchronized from Snowflake is:
  • <source_tag_name>=<source_tag_value>, for example: cost_center=sales.
  • <source_tag_name>, if no values are assigned to the tag, for example PII.
• We apply the same inheritance for source tags as the data source.
  Example 

  • If a tag was assigned to a schema in Snowflake, the tag will be registered for the related Schema, Table, Column and View assets in Data Catalog.
  • If a tag was assigned to an account in Snowflake, the tag will be registered for the related Schema, Table, Column and View assets in Data Catalog.

  For information on tags in Snowflake, go to the Snowflake documentation.

• Don't change the source tags in Data Catalog, as the changes are not pushed to the data source. I If you make changes to the tags in the data source and synchronize the data source again, your updates will be overwritten with the information from the data source.

By default, we read the Snowflake source tags from the <database_name>.INFORMATION_SCHEMA.tag_ references. This is possible with the minimum required permissions for the metadata scan.
To increase the performance of the Snowflake metadata synchronization, we can also read the Snowflake source tags from the SNOWFLAKE.ACCOUNT_USAGE schema. This can be configured in the Edge JDBC Ingestion capability as an other property with name tags-strategy and value SINGLE_CALL. Note that this method requires the SELECT permission on the SNOWFLAKE.ACCOUNT_USAGE.TAG_REFERENCES table.