What is the difference between DATABASE_MEMORY = AUTOMATIC (with
SELF_TUNING_MEM = ON) and DATABASE_MEMORY = AUTOMATIC (with SELF_TUNING_MEM = OFF)?


Alec

This information is for DB2 v9.5+ on AIX

DATABASE_MEMORY AUTOMATIC + STMM ON (and active) -> self-tuned database memory (allows STMM to change overall database memory size)
DATABASE_MEMORY AUTOMATIC + STMM OFF -> self-managed in how it grows and releases memory usage. It's the same as DATABASE_MEMORY COMPUTED.

Both AUTOMATIC and COMPUTED have the following regardless of STMM:
- database memory size is allocated based on the underlying configuration (bufferpools, etc.)
- we can grow beyond the computed size set by AUTOMATIC or COMPUTED setting if there is some requirement that wasn't configured for (ie. concurrent loads issued specifying some data buffer size that exceed utility heap + database overflow).