whichdb
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Db2 for i vs PostgreSQL

Db2 for i: The relational database built into IBM i (AS/400), integrated with the OS and object security. PostgreSQL: The extensible, standards-first open-source relational database.

key differences

  • Licensing: Db2 for i is proprietary (Proprietary commercial license); PostgreSQL is open source (permissive) (PostgreSQL License).
  • Horizontal scaling is none in Db2 for i and addon in PostgreSQL.
  • Only Db2 for i has encryption at rest, time travel.
  • Only PostgreSQL has vector search, geospatial, change data capture, pub/sub, online schema changes.

choose ibm-db2-for-i for

  • +ERP and distribution systems on IBM i
  • +Regional banking and insurance back ends
  • +Manufacturing execution and warehouse systems
  • +Exposing RPG business logic and data via SQL services and REST

best at · OLTP

choose postgresql for

  • +General-purpose application backend
  • +SaaS multi-tenant data
  • +Geospatial applications with PostGIS
  • +Semantic search alongside relational data with pgvector

best at · OLTP, Geo, Search

Db2 for iThe relational database built into IBM i (AS/400), integrated with the OS and object security.
PostgreSQLThe extensible, standards-first open-source relational database.
overview
Primary model
Relational
Relational
Also supports
Document
Document, Spatial
Type
Database engine
Database engine
Status
Active
Active
Developer
IBM
PostgreSQL Global Development Group
First release
1988
1996
Latest version
IBM i 7.6 TR2 (Jul 2026)
18.6 (Aug 13, 2026)
License
ProprietaryProprietary commercial license
Open source (permissive)PostgreSQL License
Free tier
—
✓
popularity
WhichDB Score
4.3
93.2
Rank
#410
#1
GitHub stars
–
22.6K
Stack Overflow questions
999
178.8K
scale & guarantees
Comfortable data size
Medium (≤ 10 TB)
Medium (≤ 10 TB)
Horizontal scaling
None
Addon
Multi-region
Read replicas
Read replicas
ACID
Full
Full
Consistency
Strong
Strong
Schema
Strict
Strict
Architecture
Single node, Multi primary, Shared storage
Single node, Primary replica, Client server
deployment
Self-hosted
✓
✓
Vendor-managed cloud
✓
—
Serverless
—
—
Embedded
—
—
Edge
—
—
Clouds
IBM Cloud
AWS, Google Cloud, Azure, Oracle Cloud, IBM Cloud, Alibaba Cloud
capabilities
Transactions
✓
✓
Joins
✓
✓
Secondary indexes
✓
✓
Full-text search
✓
✓
Vector search
—
✓
Geospatial
—
✓
JSON
✓
✓
Change data capture
—
✓
Triggers
✓
✓
Stored procedures
✓
✓
Materialized views
✓
✓
TTL / expiry
—
—
Pub/Sub
—
✓
Columnar storage
—
—
In-memory
—
—
Durable persistence
✓
✓
Compression
✓
✓
Encryption at rest
✓
—
Role-based access
✓
✓
Time travel
✓
—
Branching
—
—
Online schema changes
—
✓
Streaming ingest
—
—
Offline sync
—
—
Runs in WebAssembly
—
—
interfaces
Query languages
SQL, SQL PL, RPG record-level access
SQL, PL/pgSQL
Client languages
RPG, COBOL, Java, Python, JavaScript, C#, PHP
C, Java, Python, JavaScript, Go, Rust, C#, Ruby
Best for
OLTP
OLTP, Geo, Search, Content
Add more to this comparisonNot sure either fits? Try smart match

Db2 for i vs PostgreSQL: FAQ

What is the difference between Db2 for i and PostgreSQL?

Db2 for i: The relational database built into IBM i (AS/400), integrated with the OS and object security. PostgreSQL: The extensible, standards-first open-source relational database. Licensing: Db2 for i is proprietary (Proprietary commercial license); PostgreSQL is open source (permissive) (PostgreSQL License). Horizontal scaling is none in Db2 for i and addon in PostgreSQL. Only Db2 for i has encryption at rest, time travel.

When should I choose Db2 for i over PostgreSQL?

Choose Db2 for i for ERP and distribution systems on IBM i; regional banking and insurance back ends; and manufacturing execution and warehouse systems. Choose PostgreSQL for general-purpose application backend, SaaS multi-tenant data and geospatial applications with PostGIS.

Is Db2 for i or PostgreSQL more popular?

PostgreSQL ranks #1 on the WhichDB Score (93.2/100) and Db2 for i ranks #410 (4.3/100). Popularity is not fit: check the requirements that matter for your project.

Are Db2 for i and PostgreSQL open source?

No. Db2 for i is proprietary, closed-source software. Yes. PostgreSQL is open source. License: PostgreSQL License.