Database Reference
In-Depth Information
information on semaphores is also included. RAC instances write information on the intercon-
nect IP address and protocol to the trace file. This is particularly useful to verify the interconnect
addresses in Oracle9
i
, since releases prior to Oracle10
g
do not write this information to the
alert log.
On UNIX systems, each shared memory segment and semaphore set has a unique identifier.
These identifiers are listed by the command
ipcs
. Use
ipcs
-mb
to list shared memory segments
along with the owner and size.
$ ipcs -mb
IPC status from /dev/mem as of Mon Nov 19 15:30:49 MEZ 2007
T ID KEY MODE OWNER GROUP SEGSZ
Shared Memory:
m 6 0x00006000 --rw-rw-rw- root system 1928456
m
7
0xc3f37a04 --rw-r----- oracle dba 5050753024
m 8 0x0d000b59 --rw-rw-rw- root system 1440
The following section shows how to dump IPC information. The trace file is from a RAC
instance. Thus it contains not only shared memory identifiers, but also information on the
cluster interconnect, which is marked by the string “SSKGXPT” in both Oracle9
i
and Oracle10
g
.
$ sqlplus "/ as sysdba"
Connected to:
Oracle9i Enterprise Edition Release 9.2.0.8.0 - 64bit Production
With the Real Application Clusters option
SQL> ORADEBUG SETMYPID
Statement processed.
SQL> ORADEBUG IPC
Information written to trace file.
SQL> ORADEBUG TRACEFILE_NAME
/var/opt/oracle/udump/fhs91_ora_1065152.trc
The following trace file excerpts include the relevant sections. Note how the shared memory
identifier 7 matches the output of the command
ipcs
depicted earlier.
Shared Memory:
ID KEY
7
0xc3f37a04
The following trace file section indicates that the IP address 172.16.0.1 is used as the RAC
interconnect address. The interconnect protocol is UDP (user datagram protocol).
SSKGXPT 0x1028d484 flags SSKGXPT_READPENDING active network 0
info for network 0
socket no 8 IP
172.16.0.1
UDP
52608
ORADEBUG
may also be used with ASM instances. Following is an example that illustrates the
use of semaphores by an ASM instance:
