Preserving table hierarchy in Instance Data Replication

  • Release version: Yokohama
  • Updated January 30, 2025
  • 2 minutes to read
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    Summary of Preserving table hierarchy in Instance Data Replication

    When using Instance Data Replication (IDR) in ServiceNow, it is crucial to decide how to handle parent-child table hierarchies before creating replication sets. Determining whether to preserve the hierarchy and choosing a replication strategy impacts how data is replicated across instances, specifically in terms of which table columns and records are included on the consumer side.

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    Replication Strategies

    • Strategy 1: Preserve the entire hierarchy and replicate child columns
      This approach replicates data from each child table by creating outbound entries with sysclassname filters for each child table. For example, replicating the Task table along with Incident, Problem, and Change Request tables ensures all child table columns are included on the consumer. Records are inserted into the corresponding child tables, maintaining full hierarchy and data fidelity.
    • Strategy 2: Preserve the hierarchy, but don't replicate child columns
      Here, only the parent table columns are replicated, but the hierarchy is preserved by including the sysclassname field in the Included Fields list. This maintains the distinction between parent and child records on the consumer instance, but excludes columns unique to child tables.
    • Strategy 3: Ignore the hierarchy, and only replicate parent table data
      This method replicates only the parent table records and excludes the sysclassname field. As a result, all replicated records on the consumer are treated as parent records, and no child table columns or distinctions are preserved. This is useful when you want a simplified view for reporting or auditing.

    Practical Considerations for ServiceNow Customers

    Choosing the appropriate strategy depends on your replication goals:

    • If you require full fidelity of hierarchical data across instances, including all child table details, use Strategy 1.
    • If you want to maintain record type distinctions but only need parent table data replicated, Strategy 2 is appropriate.
    • For simpler replication scenarios where child data is not needed, Strategy 3 reduces complexity by treating all records as parent records.

    Understanding these options helps you configure replication sets effectively, ensuring your data remains consistent and usable according to your business needs.

    Decide if you want to replicate a parent-child table hierarchy and what strategy to use for replicating the data in Instance Data Replication (IDR).

    Before you create a replication set, determine if the table that you want to replicate is part of a parent-child table hierarchy. If it is, decide if you want to preserve the hierarchy and whether to replicate the data from the parent perspective (retaining only columns belonging to the parent table) or from the child perspective (retaining all columns that belong to the child tables). Review the following available strategies.

    Strategy 1: Preserve the entire hierarchy and replicate child columns
    You can preserve the entire hierarchy, including all of the child table columns, by creating an outbound entry for each child table, and specifying a sys_class_name filter for each child table.

    For example, to replicate the Task table and ensure that all of the columns from all of the child tables are included, specify the following:

    Table 1. Outbound entries
    Table Filter
    Task sys_class_name=task
    Incident sys_class_name=incident
    Problem sys_class_name=problem
    Change Request sys_class_name=change

    And so forth, for all of the child tables, including filters with each table for the sys_class_name.

    With this strategy, records are inserted into each child table on the consumer, including data from the columns that belong to each child table on the producer.

    Strategy 2: Preserve the hierarchy, but don't replicate child columns
    To preserve the hierarchy but only replicate columns from the parent table, replicate the parent table and include the Class Name [sys_class_name] field in the Included Fields list. Including the Class Name field maintains the distinction between parent and child records on the consumer instance.
    For example, if you want to replicate the Task table and its children (Incident, Problem, Change Request), but only replicate the columns that belong to the Task table, specify the following:
    Table 2. Outbound entry
    Table Included Fields
    Task Class Name

    In this strategy, the sys_class_name column on the consumer Task table receives entries for the parent table (task) and child tables (incident, problem, and change), and records are inserted into the respective child tables on the consumer. However, without the sys_class_name filter, the columns that are unique to each child table are not replicated.

    Strategy 3: Ignore the hierarchy, and only replicate parent table data
    To ignore the hierarchy and only replicate parent records, replicate the parent table and exclude the Class Name [sys_class_name] field from the Included Fields list. Excluding the Class Name field removes the distinction between parent and child records on the consumer instance. All replicated records on the consumer will be parent table records.
    For example, if you want to replicate records from the Task table and simply consider all records as tasks for reporting or auditing purposes, specify the following:
    Table 3. Outbound entry
    Table Included Fields
    Task Any fields except for Class Name

    In this strategy, when you replicate the Task table, all replicated records have a value of task in the sys_class_name column, and no columns belonging to the child tables are replicated.