Key Differences between AMM and ASMM & 19c Best Practices
AMM (Automatic Memory Management) - (MEMORY_TARGET):
How it works: Oracle automatically distributes memory between SGA and PGA.
Pros: Simplest to configure; dynamic resizing across both areas.
Cons: Incompatible with HugePages, which are crucial for performance in large systems. Can have issues with /dev/shm on Linux.
Recommendation: Suitable for testing or small instances (< 4GB SGA).
ASMM (Automatic Shared Memory Management) - (SGA_TARGET):
How it works: Oracle automatically tunes SGA components (buffer cache, shared pool) but PGA is managed separately.
Pros: Recommended for production; supports HugePages for better performance, reduces OS paging.
Cons: Requires manual tuning of PGA_AGGREGATE_TARGET.
19c Context: Oracle 19c generally recommends ASMM (using SGA_TARGET and PGA_AGGREGATE_TARGET) for production environments over AMM to ensure optimal memory management and stability
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