Last updated on JANUARY 23, 2017
Applies to:
Oracle Net Services - Version 11.1.0.6 to 11.2.0.3 [Release 11.1 to 11.2]Oracle Net Services - Version 12.1.0.2 to 12.1.0.2 [Release 12.1]
HP-UX PA-RISC (64-bit)
Generic UNIX
Symptoms
After upgrading to 11g Oracle functionality bypasses the /etc/hosts file when resolving hostnames to IPs and instead query the DNS server. This can introduce some delay in establishing a connection to a remote host compared with 10g.
SQL*Plus and tnsping show this behavior but this delay can appear also when opening a dblink or anytime tcpip connections are established by the Oracle Network layer.
This happens even if Name Server Switch configuration (nsswitch) specifies the hosts file prior to dns lookups:
hosts: files [NOTFOUND=continue] dns
or only:
hosts: files
If we obtain truss/tusc trace for a SQL*Plus connection we find the following sequence of OS system calls:
On 10g after reading the nsswitch.conf file, library "libnss_files.so" is loaded then /etc/hosts is read and the socket is opened:
open("/etc/nsswitch.conf", O_RDONLY|0x800, 0666) = 5
ioctl(5, TCGETA, 0x9fffffffffffaca0) ERR#25 ENOTTY
read(5, "# \n# / e t c / n s s w i t c ".., 8192) = 92
read(5, 0x60000000001e6078, 8192) = 0
close(5) = 0
open("/usr/lib/hpux64/libnss_files.so.1", O_RDONLY|0x800, 0) = 5
fstat(5, 0x9fffffffffffa720) = 0
pread(5, "7fE L F 0202010101\0\0\0\0\0\0\0".., 1024, 0) = 1024
stat("/usr/lib/hpux64/dpd", 0x9fffffffffff9cd0) = 0
open("/usr/lib/hpux64/dpd/libnss_files.so.1.bpd", O_RDONLY|0x800, 0) ERR#2 ENOENT
getuid() = 305 (305)
getgid() = 303 (303)
mmap(NULL, 85872, PROT_READ|PROT_EXEC, MAP_SHARED|MAP_SHLIB, 5, 0) = 0xc0000000008d8000
mmap(NULL, 3159, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_SHLIB, 5, 131072) = 0x9fffffffbf63d000
close(5) = 0
getuid() = 305 (305)
getgid() = 303 (303)
open("/etc/hosts", O_RDONLY|0x800, 0666) = 5
ioctl(5, TCGETA, 0x9fffffffffffac30) ERR#25 ENOTTY
read(5, "# / e t c / h o s t s \n# \n# ".., 8192) = 8192
lseek(5, 18446744073709549410, SEEK_CUR) = 5986
close(5) = 0
socket(AF_INET, SOCK_STREAM, 0) = 5
connect(5, 0x60000000001f0680, 16) = 0
getsockname(5, 0x9fffffffffffb750, 0x9fffffffffffb740) = 0
getsockopt(5, SOL_SOCKET, SO_SNDBUF, 0x9fffffffffffb890, 0x9fffffffffffb894) = 0
getsockopt(5, SOL_SOCKET, SO_RCVBUF, 0x9fffffffffffb890, 0x9fffffffffffb894) = 0
setsockopt(5, 0x6, TCP_NODELAY, 0x9fffffffffffb89c, 4) = 0
But on 11g after reading the nsswitch.conf library "libnss_dns.so" is loaded then /etc/resolv.conf (which specifies available domain name servers) is read and much later a socket for TCP/IP (SOCK_STREAM) is opened. :
open("/etc/nsswitch.conf", O_RDONLY|0x800, 0666) = 5
ioctl(5, TCGETA, 0x9fffffffffffa360) ERR#25 ENOTTY
read(5, "# \n# / e t c / n s s w i t c ".., 8192) = 92
read(5, 0x60000000001c9058, 8192) = 0
close(5) = 0
open("/usr/lib/hpux64/libnss_dns.so.1", O_RDONLY|0x800, 0) = 5
fstat(5, 0x9fffffffffff9de0) = 0
pread(5, "7fE L F 0202010101\0\0\0\0\0\0\0".., 1024, 0) = 1024
stat("/usr/lib/hpux64/dpd", 0x9fffffffffff9390) = 0
open("/usr/lib/hpux64/dpd/libnss_dns.so.1.bpd", O_RDONLY|0x800, 0) ERR#2 ENOENT
getuid() = 305 (305)
getgid() = 303 (303)
mmap(NULL, 49440, PROT_READ|PROT_EXEC, MAP_SHARED|MAP_SHLIB, 5, 0) = 0xc00000000b054000
mmap(NULL, 800, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_SHLIB, 5, 65536) = 0x9fffffffbf68d000
close(5) = 0
getuid() = 305 (305)
getgid() = 303 (303)
getuid() = 305 (305)
getgid() = 303 (303)
open("/test/local/oracle/11.1.0.7/lib/libdl.so.1", O_RDONLY|0x800, 0) ERR#2 ENOENT
open("/test/local/oracle/11.1.0.7/lib32/libdl.so.1", O_RDONLY|0x800, 0) ERR#2 ENOENT
getuid() = 305 (305)
getgid() = 303 (303)
open("/usr/lib/hpux64/libdl.so.1", O_RDONLY|0x800, 0) = 5
fstat(5, 0x9fffffffffff9cf0) = 0
read(5, "7fE L F 0202010101\0\0\0\0\0\0\0".., 64) = 64
close(5) = 0
socket(AF_INET, SOCK_DGRAM, 0) = 5
ioctl(5, SIOCGIFNUM, 0x9fffffffffff9680) = 0
ioctl(5, SIOCGIFCONF, 0x9fffffffffff9690) = 0
socket(AF_INET6, SOCK_DGRAM, 0) = 6
ioctl(6, SIOCGLIFNUM, 0x9fffffffffff9684) = 0
ioctl(6, SIOCGLIFCONF, 0x9fffffffffff96a0) = 0
ioctl(5, SIOCGIFFLAGS, 0x9fffffffffff96b0) = 0
close(5) = 0
close(6) = 0
gettimeofday(0x9fffffffffff7dd0, NULL) = 0
getpid() = 22968 (22967)
open("/etc/resolv.conf", O_RDONLY|0x800, 0666) = 5
ioctl(5, TCGETA, 0x9fffffffffff7da0) ERR#25 ENOTTY
read(5, "d o m a i n t e s t . c o m \n".., 8192) = 453
read(5, 0x60000000001dddf8, 8192) = 0
close(5) = 0
................
.............
socket(AF_INET, SOCK_STREAM, 0) = 5
connect(5, 0x60000000001eba50, 16) = 0
getsockname(5, 0x9fffffffffff9da0, 0x9fffffffffff94c0) = 0
getsockopt(5, SOL_SOCKET, SO_SNDBUF, 0x9fffffffffffa000, 0x9fffffffffffa004) = 0
getsockopt(5, SOL_SOCKET, SO_RCVBUF, 0x9fffffffffffa000, 0x9fffffffffffa004) = 0
setsockopt(5, 0x6, TCP_NODELAY, 0x9fffffffffffa00c, 4) = 0
Changes
Nothing was changed in the configuration of the OS, only the upgrade from Oracle 10g to 11g was done.
Cause
Sign In with your My Oracle Support account |
|
Don't have a My Oracle Support account? Click to get started |
My Oracle Support provides customers with access to over a
Million Knowledge Articles and hundreds of Community platforms