ORA-27102: out of memory
OracleWhat does it mean?
During startup, the Oracle instance could not allocate the shared memory (SGA) segment it requested from the operating system. Usually seen together with ORA-27102 and a lower-level OSD/Linux error code (e.g. Linux-x86_64 Error: 28: No space left on device).
Why does it happen?
The memory requested for the SGA exceeds the kernel's shared memory limits (shmmax, shmall); the server lacks sufficient physical RAM/swap; or the HugePages configuration is missing/insufficient so a large SGA cannot be allocated. Common after SGA_MAX_SIZE is increased.
How to fix it
Increase the kernel shared memory parameters: set kernel.shmmax and kernel.shmall in /etc/sysctl.conf to cover the SGA and run sysctl -p. If you use HugePages, calculate and set vm.nr_hugepages based on the SGA. Check total RAM and swap on the server; if necessary, lower SGA_MAX_SIZE / SGA_TARGET.