onstat -g seg command: Print shared memory segment statistics

Use the onstat -g seg command to show the statistics for shared memory segments.

This command shows how many segments are attached and their sizes. You can run the onstat -g seg command on a dump file that was created without the buffer pool.

Figure 1: Syntax:

Example output

Figure 2: onstat -g seg command output

Segment Summary:
id         key        addr     size       ovhd     class blkused  blkfree 
720914    52e44801  44000000 4390912    248812  R    1072     0      
753683    52e44802  44430000 131072000  769136  V    22573    9427    
819221    52e44803  4c130000 66027520  1        B    16120    0      
851990    52e44804  50028000 83648512  1        B    20422    0      
Total:    -          -       285138944 -        -    60187    9427
Virtual segment low memory reserve (bytes):4194304 
Low memory reserve used 0 times and used maximum block size 0 bytes

id         key        addr     size       ovhd     class blkused  blkfree 
8945678    52604801   44000000 133652480  1006264  R     32627    3       
8978447    52604802   4bf76000 131072000  769136   V     17181    14819   
Total:     -          -        264724480  -        -     49808    14822   

   (* segment locked in memory)
Virtual segment low memory reserve (bytes):4194304 
Low memory reserve used 0 times and used maximum block size 0 bytes

Output description

id: The ID of the shared memory segment
key: The shared memory key that is associated with the shared memory segment ID
addr: The address of the shared memory segment
size: The size of the shared memory segment in bytes
ovhd: The size of the shared memory segment control information (overhead) in bytes
class: The class of the shared memory segment (B is for Buffferpool, R is for Resident, V is for Virtual, VX is for Virtual Extended, and M is for Message.); The class of the shared memory segment (R is for Resident, V is for Virtual, VX is for Virtual Extended, and M is for Message.)
blkused: The number of blocks of used memory
blkfree: The number of blocks of free memory
Virtual segment low memory reserve (bytes): The size of reserved memory for use when critical activities are needed and the server has limited free memory, specified in bytes (You specify reserved memory in the LOW_MEMORY_RESERVE configuration parameter.)
Low memory reserve used 0 times and used maximum block size 0 bytes): The number times that the server used the reserved memory and the maximum memory needed