AIMemory Storage Engine

The AIMemory engine (aimem) stores all data in off-heap memory using B+ tree structures. Data is volatile and lost on node shutdown. Use this engine for caching, temporary tables, or workloads where persistence is unnecessary.

Memory Architecture

Key characteristics:

• Memory allocated in segments, starting with initSizeBytes and expanding on demand
• Up to 16 segments per data region, minimum 256 MB per segment expansion
• Default page size: 16 KB (configurable from 1 KB to 16 KB, must be power of 2)
• 32-byte overhead per page for header and locking structures

Profile Configuration

Property	Default	Description
engine	-	Must be "aimem"
initSizeBytes	Dynamic	Initial memory allocation. Defaults to maxSizeBytes value
maxSizeBytes	Dynamic	Maximum memory. Defaults to max(256 MB, 20% of physical RAM)

Engine Configuration

Page size is configured at the engine level and applies to all aimem profiles:

Property	Default	Description
pageSizeBytes	16384	Page size in bytes (1024 to 16384, power of 2)

# Configure engine-level page size
node config update ignite.storage.engines.aimem.pageSizeBytes=8192

Configuration Example

{
  "ignite": {
    "storage": {
      "profiles": [
        {
          "engine": "aimem",
          "name": "cache_profile",
          "initSizeBytes": 536870912,
          "maxSizeBytes": 1073741824
        }
      ]
    }
  }
}

# CLI equivalent
node config update "ignite.storage.profiles:{cache_profile{engine:aimem,maxSizeBytes:1073741824}}"

Usage

-- Create a zone using the volatile profile
CREATE ZONE cache_zone
    WITH PARTITIONS=10, REPLICAS=2,
    STORAGE PROFILES ['cache_profile'];

-- Create a table for session data (acceptable to lose on restart)
CREATE TABLE sessions (
    session_id UUID PRIMARY KEY,
    user_id INT,
    data VARCHAR,
    expires_at TIMESTAMP
) ZONE cache_zone STORAGE PROFILE 'cache_profile';