Short text
Maximum segment size for shared memory
Parameter Description
Restricts the maximum size of shared memory segments used by Extended Segments (ES) administration.
If an operating system has performance limitations when handling “large” shared memory segments, the ES layer can be forced with this parameter to avoid allocating shared memory segments exceeding the given size.
The only operating system where customers have set this parameter in order to increase ES performance is HP-UX.
“Rule of thumb” settings reported by HP consultants:
es/max_seg_size = 1024 for servers with EM memory <= 32 GB
es/max_seg_size = 2048 for servers with EM memory <= 64 GB
es/max_seg_size = 4096 for servers with EM memory > 64 GB
Note: “EM memory” here refers to the total size of EM memory specified via parameter em/initial_size_MB
Application Area
BC-CST-MM (Memory Management)
Parameter Unit
MB
Default Value
0 (means: no restriction on maximum segment size)
Who is permitted to make changes?
Customer
Operating System Restrictions
(potentially necessary only on HP-UX)
Database System Restrictions
none
