Its very important for DBA to calculate the size of oracle process.
Most of the time DBAs uses OS utilities to count the size of Oracle process.
The process in memory is comprise of following.
- shared memory (the SGA)
- shared libraries (both public, and private)
- private data (referred to as DATA, or heap)
- the executable (referred to as TEXT)
Unfortunately, commands such as ‘ps’ and ‘top’ include TEXT sizes when measuring private data.
Few OS provides very good utilities which provide more accurate data.Examples are PMAP , GLANCE etc.
Here is the example to prove it.
oracle@oaxgs36$ ps -eafl | grep 12456
0 O oracle 12456 12451 10 78 20 ? 153449 22:34:37 ? 422:43 oraclexgs (DESCRIPTION=(LOCAL=YES)(
PS command show the size 153449 kb means around 153 MB.
oracle@oaxgs36$ prstat | grep 12456
12456 oracle 1199M 1130M sleep 60 0 7:01:54 9.9% oracle/11
PRSTAT command shows the size 1199 MB
oracle@oaxgs36$ pmap -x 12456
12456: oraclexgs (DESCRIPTION=(LOCAL=YES)(ADDRESS=(PROTOCOL=be)))
Address Kbytes RSS Anon Locked Mode Mapped File
0000000100000000 95672 94648 - – r-x– oracle
0000000105E6C000 640 408 128 – rwx– oracle
0000000105F0C000 24 8 8 – rwx– oracle
0000000105F12000 3992 216 208 – rwx– [ heap ]
0000000380000000 1048592 1048592 - 1048592 rwxsR [ ism shmid=0x2700003d ]
FFFFFFFF74200000 64 16 16 – rwx– [ anon ]
FFFFFFFF7FFB2000 312 72 72 – rw— [ stack ]
—————- ———- ———- ———- ———-
total Kb 1223432 1163592 4576 1048592
PMAP command shows total size 1220 MB but gives the breakup.
0000000105F12000 3992 216 208 – rwx– [ heap ] – Around 4 MB
0000000380000000 1048592 1048592 - 1048592 rwxsR [ ism shmid=0x2700003d ] – Around 1GB Shared Memory
SGA is of around 1GB size.The shared memory segment identifier is 0×2700003d which you can relate with ipcs -m command.
This highlights that the private data area of approx 150kB cannot be measured accurately from standard operating system utilities such as ‘ps’ and ‘top’ whereas ‘pmap’ allows a more accurate figure to be determined.
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