3833760 - Db2start fails - OSERR   : ENOMEM (12) "Not enough space"

db2start fails with a memory allocation error. The db2diag.log reports SQLO_NOSEG / DIA8305C ("No Storage Available for allocation") and the operating system reports ENOMEM (12) "Not enough space" when Db2 attempts to allocate the database shared memory set.

Example:

2026-10-03-17.12.42 LEVEL: Warning (OS)
FUNCTION: DB2 UDB, SQO Memory Management, sqloMemCreateSingleSegment
CALLED: OS, -, shmget
OSERR: ENOMEM (12) "Not enough space"

MESSAGE: ZRC=0x850F0005=SQLO_NOSEG
"No Storage Available for allocation"
DIA8305C Memory allocation failure occurred.

Failed to allocate the desired database shared memory set.
The configured DATABASE_MEMORY plus desired overflow may have exceeded INSTANCE_MEMORY or the maximum shared memory on the system.

Desired database shared memory set size is (bytes):
Example: 190909054976 

Db2 LUW IBM

DB2 LUW, DB2START, INSTANCE_MEMORY, DATABASE_MEMORY, SQLO_NOSEG, DIA8305C, ENOMEM, shared memory, memory allocation, shmget, DB6, SAP , KBA , BC-DB-DB6 , DB2 Universal Database for Unix / NT , Problem