Oracle 26ai new chapter in memory architecture (MGA)

🚀 Understanding Oracle’s Managed Global Area (MGA): A New Chapter in Memory Architecture

Alireza Kamrani

While exploring Oracle’s latest AI Database 26ai documentation (Oracle Docs → Memory Architecture Diagram), one feature that stands out is the Managed Global Area (MGA) — a modern evolution in Oracle’s memory design that adds a new layer of flexibility and intelligence.

What Is the Managed Global Area (MGA)?

The MGA (Managed Global Area) is a semi-shared memory region that bridges the gap between the System Global Area (SGA) and the Program Global Area (PGA).



Unlike the SGA (which is fully shared across all processes) or the PGA (which is private to a

single process), the MGA is shared selectively — only among a trusted set of Oracle processes.
Its goal is to let certain background or foreground processes share data and structures dynamically, without the rigidity of static SGA allocations.


The Power of “Namespaces” in MGA:

The key innovation behind MGA is its namespace-based architecture that inherent from Linux namespace concepts.

• Each namespace represents a logical memory domain within the MGA — a kind of “sandbox” or shared memory context that related processes can attach to.
• These namespaces are modular and dynamic — Oracle components can create, attach, or drop them as needed.
• For example, a namespace could be used for:
• A parallel query execution team sharing intermediate results
• A metadata caching group
• A vector or AI operator needing temporary shared state
• Because each namespace is isolated, Oracle can manage access, size, and cleanup independently — keeping the system both flexible and safe.

This namespace-based sharing allows Oracle to optimize memory for on-demand collaboration among processes, without the overhead or risk of global sharing.

Why Oracle Added MGA:

MGA fills an architectural gap between static and private memory management:
• Dynamic Sharing – Enables processes to share temporary memory safely using namespaces.
• Elastic & Modular – Memory segments can be created, resized, or destroyed dynamically — no instance restart required.
• Controlled Scope – Only approved processes can attach to a namespace; it’s not globally visible like the SGA.
• Governed by PGA Limits – MGA usage counts toward the PGA aggregate limit, ensuring unified memory control.
• Recoverable & Flexible – Enables better resilience and cleaner memory lifecycle management, especially for transient workloads.

How MGA Fits in Oracle’s Memory Hierarchy:

Here’s how Oracle’s three main memory areas relate:

System Global Area (SGA)
Fully shared across the entire database instance.
Used for caches, buffer cache, and shared SQL or library cache.
Mostly static — memory is allocated at instance startup.


Program Global Area (PGA)
Private to each server or background process.
Used for sorts, session state, and runtime working memory.
Dynamically allocated and freed per session or process.

Managed Global Area (MGA)
Semi-shared — shared only among a trusted set of Oracle processes.
Organized into namespaces, each acting as an isolated memory domain.
Enables dynamic, temporary sharing of data structures between related processes.
Elastic and modular — namespaces can be created, resized, and dropped on demand.
Memory consumption is governed under PGA aggregate limits for unified control.

Why This Matters for DBAs & Architects:

As Oracle continues to evolve toward AI-driven workloads and adaptive memory management, understanding MGA becomes essential:
• Monitor MGA memory usage within overall PGA limits.
• Expect more internal Oracle components (e.g., vector search, AI operators, and parallel processing) to leverage MGA namespaces for optimized data sharing.
• When tuning or troubleshooting, remember that some shared structures may now live in MGA namespaces rather than the SGA.

Finally, the Managed Global Area (MGA) brings namespace-based intelligence and modularity to Oracle’s memory system.
It’s not just shared memory; it’s structured, scoped, and smart memory — a foundation for Oracle’s next-generation database performance.