The Maximum Value That Can Be Set to SGA_MAX_SIZE and SGA_TARGET in 19c

刘泽宇

现象：
When DB startup is attempted, the following message appears in the alert log and the DB cannot be started:

Example:

Starting ORACLE instance (normal) (OS id: 12183)
2025-03-17T20:59:21.360860+09:00
System cannot support SGA size of 230 GB.
2025-03-17T20:59:21.360909+09:00
Total system memory configured is 252 GB.
2025-03-17T20:59:21.360938+09:00
Instance maximum shared memory size should be less than 227 GB.

The following errors are returned in sqlplus:

ORA-27104: system-defined limits for shared memory was misconfigured

原因：
19c cannot allocate more than 90% of physical memory to the SGA.
This is the expected behavior.



处理方法：
Set sga_max_size and sga_target to a value less than 90% of physical memory.


Also review the following documents for configuring the SGA:

Best Practices for Database Memory (SGA) Settings (Doc ID 3068352.1)

It is recommended that you follow best practices.