10 InterSystems Interview Questions and Answers

InterSystems is a leading provider of data management, integration, and analytics solutions, known for its high-performance database management systems and interoperability platforms. Its technologies are widely adopted in healthcare, finance, and other industries that require robust, scalable, and reliable data solutions. With a focus on enabling seamless data exchange and real-time analytics, InterSystems products are essential for organizations aiming to leverage their data for strategic advantage.

This article offers a curated selection of interview questions designed to test your knowledge and proficiency with InterSystems technologies. By working through these questions, you will gain a deeper understanding of key concepts and be better prepared to demonstrate your expertise in a professional setting.

InterSystems Interview Questions and Answers

1. Explain how to use SQL within InterSystems IRIS.

InterSystems IRIS is a data platform that supports SQL for querying and managing data. It provides a robust SQL engine for seamless integration with SQL-based applications. To use SQL within InterSystems IRIS, connect to the database using standard SQL clients or InterSystems IRIS’s tools, and execute SQL queries to interact with the data.

Example:

import irisnative

# Establish a connection to the InterSystems IRIS database
connection = irisnative.createConnection("localhost", 1972, "USER", "_SYSTEM", "SYS")

# Create an IRIS object
iris = irisnative.createIris(connection)

# Execute an SQL query to retrieve data
sql_query = "SELECT * FROM Sample.Person WHERE Age > 30"
result = iris.sql(sql_query)

# Iterate through the result set
for row in result:
    print(row)

# Close the connection
connection.close()

2. What are globals in InterSystems, and how are they used?

Globals in InterSystems are hierarchical, multidimensional arrays used for efficient data storage and management. They are accessed using a dot notation, allowing for complex data structures.

Example:

// Setting a value in a global
SET ^GlobalName("Level1", "Level2") = "Value"

// Getting a value from a global
WRITE ^GlobalName("Level1", "Level2")

Globals are used for storing application data, creating custom indexes, and temporary data storage.

3. Write a simple ObjectScript method to retrieve data from a global.

InterSystems ObjectScript is used for database and application development. To retrieve data from a global, define a method within a class that accesses the global and returns the desired data.

Example:

ClassMethod GetDataFromGlobal(globalName As %String, key As %String) As %String
{
    // Access the global and retrieve the value
    Set value = $Get(^@(globalName)(key))
    Return value
}

4. What are the key features of InterSystems IRIS that support high availability and disaster recovery?

InterSystems IRIS supports high availability and disaster recovery through features like:

• Mirroring: Provides automatic failover to a standby system.
• Sharding: Allows horizontal scaling by distributing data across servers.
• Backup and Restore: Offers online backups and quick data restoration.
• Journal Files: Records all database changes for recovery purposes.
• Data Replication: Ensures data availability across multiple nodes.

5. How does InterSystems IRIS handle data persistence and durability?

InterSystems IRIS ensures data persistence and durability through:

• Journaling: Logs all database changes for recovery.
• Write-Ahead Logging (WAL): Writes changes to a log before applying them to the database.
• Transactional Integrity: Supports ACID transactions for consistent database operations.
• Mirroring: Provides real-time data replication for high availability.
• Backup and Recovery: Offers regular backups and point-in-time recovery options.

6. Discuss the interoperability capabilities of InterSystems IRIS beyond Ensemble.

InterSystems IRIS offers advanced interoperability capabilities, including:

• Data Integration: Supports integration from various data sources.
• API Management: Enables creation and management of APIs.
• Business Process Automation: Provides tools for automating workflows.
• Event Processing: Handles real-time event monitoring and analysis.
• Interoperability Standards: Supports standards like HL7, FHIR, and DICOM.
• Scalability and Performance: Designed for large data volumes and high transaction rates.

7. Write a query to join two tables in InterSystems SQL.

In InterSystems SQL, joining tables is a common operation. An inner join returns rows with matching values in both tables.

Example:

SELECT a.column1, a.column2, b.column3
FROM TableA a
INNER JOIN TableB b ON a.id = b.id;

In this query:

• TableA is aliased as a and TableB as b.
• INNER JOIN combines rows where the id column matches in both tables.
• The SELECT statement specifies the columns to retrieve.

8. Explain the use of RESTful services in InterSystems.

InterSystems supports RESTful services, allowing developers to create web services. Key components include:

• Web Applications: Route HTTP requests to classes and methods.
• Dispatch Classes: Handle incoming HTTP requests.
• Methods: Implement RESTful endpoints.

Example:

Class MyApp.REST.Dispatch Extends %CSP.REST
{
    XData UrlMap [ XMLNamespace = "http://www.intersystems.com/urlmap" ]
    {
        <Routes>
            <Route Url="/items" Method="GET" Call="GetItems"/>
            <Route Url="/items/:id" Method="GET" Call="GetItemById"/>
        </Routes>
    }

    ClassMethod GetItems() As %Status
    {
        // Implementation to get all items
    }

    ClassMethod GetItemById(id As %String) As %Status
    {
        // Implementation to get an item by ID
    }
}

9. How do you handle transactions in InterSystems IRIS?

In InterSystems IRIS, transactions are managed using START TRANSACTION, COMMIT, and ROLLBACK commands to ensure data integrity.

Example:

TRY {
    &sql(START TRANSACTION)
    
    &sql(INSERT INTO MyTable (ID, Name) VALUES (1, 'John Doe'))
    &sql(UPDATE MyTable SET Name = 'Jane Doe' WHERE ID = 1)
    
    &sql(COMMIT)
} CATCH {
    &sql(ROLLBACK)
    WRITE "Transaction failed and has been rolled back."
}

10. Write a method to handle error trapping in ObjectScript.

Error trapping in ObjectScript uses TRY and CATCH blocks to manage exceptions.

Example:

ClassMethod ExampleMethod()
{
    TRY {
        // Code that might throw an error
        SET result = ##class(SomeClass).SomeMethod()
    }
    CATCH ex {
        // Error handling code
        WRITE "An error occurred: ", ex.DisplayString(), !
    }
}