Oracle DBA by Example. Code samples, Scripts, Reference.: March 2014

===========================
Reference
===========================

Very good reference: Network Commands Reference

Site for running commands. Just provide the IP, and run command: network-tools.com

===========================

Most Useful Network commands:

===========================
ping
telnet
netcat
tracert
netstat
lsof
ifconfig
tcpdump
mii-show
MTU and Packet size
ORA-03113 and MTU ping <IP>
D:\Users\akaplan>ping 11.222.333.444

Pinging 11.222.333.444 with 32 bytes of data:
Reply from 11.222.333.444: bytes=32 time=2ms TTL=127
Reply from 11.222.333.444: bytes=32 time=1ms TTL=127
Reply from 11.222.333.444: bytes=32 time=1ms TTL=127

Ping statistics for 11.222.333.444:
Packets: Sent = 3, Received = 3, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:

Minimum = 1ms, Maximum = 2ms, Average = 1ms

Telnet
Reference: Troubleshooting with Telnet

Useful options with telnet:
telnet <some_server> - 23 is the default port for telnet
telnet <some_server> 3000 - Try to connect on port 3000.

netcat
Reference: netcat reference
Netcat is a computer networking service for reading from and writing to network connections using TCP or UDP.

tracert <IP>
D:\Users\akaplan>tracert 111.222.333.444

Tracing route to AAA-BBB-1-CCC-2 [111.222.333.444]
over a maximum of 30 hops:

1 1 ms 1 ms 1 ms 44.555.666.1
2 1 ms 1 ms 1 ms AAA-BBB-1-CCC-2 [111.222.333.444]

Trace complete.

netstat command
netstat reference
The netstat command is used to display the TCP/IP network protocol statistics and information.

netstat flags
t - TCP active sockets
u - UDP active sockets
w - raw active sockets
x - Unix active sockets
l - Listening sockets
a - all (Active and Listening) sockets
o - timer information
p - PID/Process of the process that is using a socket
n - numeric. Do not resolve host, port, user from their numeric value.
(-n stands for Good for knowing current open connections and on which port.

netstat output fields on Linux

Proto The protocol (tcp, udp, raw) used by the socket.

Recv-Q The count of bytes not copied by the user program connected to this socket.

Send-Q The count of bytes not acknowledged by the remote host.

Local Address Address and port number of the local end of the socket.

Unless the --numeric (-n) option is specified, the socket address is resolved to

its canonical host name (FQDN), and the port number is translated into

the corresponding service name.

Foreign Address Address and port number of the remote end of the socket; analogous to "Local Address."

State The state of the socket.

Since there are no states in raw mode and usually no states used in UDP, this column may be left blank.

Normally this can be one of several values:

ESTABLISHED The socket has an established connection.

SYN_SENT The socket is actively attempting to establish a connection.

SYN_RECV A connection request has been received from the network.

FIN_WAIT1 The socket is closed, and the connection is shutting down.

FIN_WAIT2 Connection is closed, and the socket is waiting for a shutdown from the remote end.

TIME_WAIT The socket is waiting after close to handle packets still in the network.

CLOSE The socket is not being used.

CLOSE_WAIT The remote end has shut down, waiting for the socket to close.

LAST_ACK The remote end has shut down, and the socket is closed. Waiting for acknowledgement.

LISTEN The socket is listening for incoming connections. Such sockets are not included in the output unless you specify the --listening (-l) or --all (-a) option.

CLOSING Both sockets are shut down but we still don't have all our data sent.

UNKNOWN The state of the socket is unknown.

User The username or the user id (UID) of the owner of the socket.

PID/Program name Slash-separated pair of the process id (PID) and process name of the process that owns the socket. --program causes this column to be included. You will also need superuser privileges to see this information on sockets you don't own.

sudo netstat -plnt
List tcp ports that are being listened on, along with the name of each listener's daemon and its PID.
sample output:
sudo netstat -plnt
Active Internet connections (only servers)

Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 0.0.0.0:3306 0.0.0.0:* LISTEN 3686/mysqld
tcp 0 0 :::443 :::* LISTEN 2218/httpd
tcp 0 0 :::80 :::* LISTEN 2218/httpd
tcp 0 0 :::22 :::* LISTEN 1051/sshd

netstat -ano
List all ports with timer info.
sample output on Linux

Proto Recv-Q Send-Q Local Address Foreign Address State Timer
tcp 0 0 0.0.0.0:199 0.0.0.0:* LISTEN off (0.00/0/0)
tcp 0 0 127.0.0.1:2381 0.0.0.0:* LISTEN off (0.00/0/0)
tcp 0 0 127.0.0.1:2301 0.0.0.0:* LISTEN off (0.00/0/0)
tcp 0 0 10.666.3.152:2301 0.0.0.0:* LISTEN off (0.00/0/0)
tcp 0 0 111.666.222.1:2301 0.0.0.0:* LISTEN off (0.00/0/0)
tcp 0 0 127.0.0.1:9494 127.0.0.1:32802 ESTABLISHED off (0.00/0/0)
tcp 4 0 55.227.3.555:55118 55.227.3.555:199 CLOSE_WAIT off (0.00/0/0)
tcp 0 0 127.0.0.1:5302 127.0.0.1:32775 ESTABLISHED keepalive (3334.13/0/0)

netstat -a sample output on Linux

Proto Recv-Q Send-Q Local Address Foreign Address State

tcp 0 0 *:hacl-cfg *:* LISTEN

tcp 0 0 localhost.localdomain:2381 *:* LISTEN
tcp 0 0 localhost.localdomain:2301 *:* LISTEN
tcp 0 0 kuk-lol-1-cdc-1:2301 *:* LISTEN
tcp 0 0 111.666.222.1:2301 *:* LISTEN
tcp 0 0 localhost.localdomain:9494 localhost.localdomain:32802 ESTABLISHED
tcp 4 0 kuk-lol-1-cdc-1:55118 kuk-lol-1-cdc-1:smux CLOSE_WAIT
tcp 0 0 localhost.localdom:hacl-cfg localhost.localdomain:32775 ESTABLISHED

Oracle on Linux
netstat -plnt | grep 1521
(Not all processes could be identified, non-owned process info
will not be shown, you would have to be root to see it all.)
tcp 0 0 0.0.0.0:1521 0.0.0.0:* LISTEN -

netstat -ano | grep 1521
tcp 0 0 172.19.242.20:60414 172.19.242.20:1521 ESTABLISHED off (0.00/0/0)
tcp 0 0 172.19.242.20:1521 172.19.242.20:60419 ESTABLISHED keepalive (2272.24/0/0)
tcp 0 0 172.19.242.20:26383 172.19.242.20:1521 ESTABLISHED off (0.00/0/0)
tcp 0 0 172.19.242.20:26360 172.19.242.20:1521 ESTABLISHED off (0.00/0/0)
tcp 0 0 172.19.242.20:1521 172.19.242.20:26383 ESTABLISHED keepalive (7183.74/0/0)
tcp 0 0 172.19.242.20:1521 172.19.242.20:63903 ESTABLISHED keepalive (3879.65/0/0)
tcp 0 0 172.19.242.20:1521 172.19.242.20:60413 ESTABLISHED keepalive (2272.42/0/0)
tcp 0 0 172.19.242.20:65271 172.19.242.20:1521 ESTABLISHED off (0.00/0/0)
tcp 0 0 172.19.242.20:18177 172.19.242.20:1521 ESTABLISHED off (0.00/0/0)
tcp 0 0 172.19.242.20:26274 172.19.242.20:1521 TIME_WAIT timewait (14.60/0/0)
tcp 0 0 172.19.242.20:19698 172.19.242.20:1521 ESTABLISHED off (0.00/0/0)
tcp 0 0 172.19.242.20:1521 172.19.242.20:60421 ESTABLISHED keepalive (2272.27/0/0)
tcp 0 0 172.19.242.20:60259 172.19.242.20:1521 ESTABLISHED off (0.00/0/0)

netstat -ano | grep 1521 | grep keep
tcp 0 0 172.19.242.20:1521 172.19.242.20:21059 ESTABLISHED keepalive (3971.96/0/0)
tcp 0 0 172.19.242.20:1521 172.19.242.20:65271 ESTABLISHED keepalive (1977.41/0/0)
tcp 0 0 172.19.242.20:1521 172.19.242.20:17904 ESTABLISHED keepalive (5046.05/0/0)
tcp 0 0 172.19.242.20:1521 172.19.242.20:19687 ESTABLISHED keepalive (3513.32/0/0)
tcp 0 0 172.19.242.20:1521 172.19.242.20:21065 ESTABLISHED keepalive (3972.04/0/0)
tcp 0 0 172.19.242.20:1521 172.19.242.20:25412 ESTABLISHED keepalive (5916.66/0/0)
tcp 0 0 172.19.242.20:1521 172.19.242.20:27742 ESTABLISHED keepalive (7185.41/0/0)
tcp 0 0 172.19.242.20:1521 172.19.242.20:13877 ESTABLISHED keepalive (4141.11/0/0)
tcp 0 0 172.19.242.20:1521 172.19.242.20:60429 ESTABLISHED keepalive (1524.39/0/0)
tcp 0 0 172.19.242.20:1521 172.19.242.20:27745 ESTABLISHED keepalive (7185.46/0/0)
tcp 0 0 172.19.242.20:1521 172.19.242.20:63721 ESTABLISHED keepalive (3106.11/0/0)
tcp 0 0 172.19.242.20:1521 172.19.242.20:27743 ESTABLISHED keepalive (7185.43/0/0)
tcp 0 0 172.19.242.20:1521 172.19.242.20:60258 ESTABLISHED keepalive (1524.05/0/0)
tcp 0 0 172.19.242.20:1521 172.19.242.20:18177 ESTABLISHED keepalive (5075.28/0/0)
tcp 0 0 172.19.242.20:1521 172.19.242.20:63888 ESTABLISHED keepalive (3130.35/0/0)

iu@lka-mob-1-aps-1:~/workarea>% lsof -i@lka-mob-1-aps-1 | grep 21059

java 30629 iu 165u IPv4 781945850 0t0 TCP lka-mob-1-aps-1:19694->lka-mob-1-aps-1:ncube-lm (ESTABLISHED)

iu@lka-mob-1-aps-1:~/workarea>% lsof -i@lka-mob-1-aps-1 | grep 65271

java 30629 iu 165u IPv4 781945850 0t0 TCP lka-mob-1-aps-1:19694->lka-mob-1-aps-1:ncube-lm (ESTABLISHED)

iu@lka-mob-1-aps-1:~/workarea>% lsof -i@lka-mob-1-aps-1 | grep 17904

java 17501 iu 145u IPv4 781647249 0t0 TCP lka-mob-1-aps-1:60247->lka-mob-1-aps-1:ncube-lm (ESTABLISHED)

iu@lka-mob-1-aps-1:~/workarea>% lsof -i@lka-mob-1-aps-1 | grep 19687

java 47682 iu 137u IPv4 745088409 0t0 TCP lka-mob-1-aps-1:65271->lka-mob-1-aps-1:ncube-lm (ESTABLISHED)

iu@lka-mob-1-aps-1:~/workarea>% netstat -ano | grep 1521 | grep keep | wc -l
140

In this case - there is an java executable, running many processes, that are constantly connected to Oracle.

kepalive - The timer column
Reference
netstat -o output
tcp keepalive

Example: keepalive (6176.47/0/0)
The timer column has two fields
<1st field> <2nd field>

The 1st field can have three values:
keepalive - when the keepalive timer is ON for the socket
on - when the retranmission timer is ON for the socket
off - none of the above is ON

The 2nd field has three sub-fields, which are keepalive parameters.

(6176.47/0/0) -> (a/b/c)
a = Timer value (keepalive/retransmission timer, depending on first field)
b = Number of retransmissions that have occurred
c = Number of keepalive probes that have been sent

These paranmeters are configured in the file /etc/sysctl.conf.
Three parameters related to keepalive:
net.ipv4.tcp_keepalive_time
net.ipv4.tcp_keepalive_intvl
net.ipv4.tcp_keepalive_probes

The net.ipv4.tcp_keepalive_time parameter is the time before the first keepalive packet is sent out.
As long as there is TCP/IP socket communications going on, no keepalive packets are needed, but if the amount of time in seconds specified in net.ipv4.tcp_keepalive_time passes without any communication on a TCP/IP socket connection, then the Linux OS will begin sending keepalive packets.
Once keepalive packets begin being sent out, they will be sent every net.ipv4.tcp_keepalive_intvl time (in seconds).
Keepalive packets are a two-way exchange.
When one device sends a keepalive packet to another, the receiving device sends a quick acknowledgement packet back.
This way, both devices know the communication link between them is OK.
If the device sending the keepalive packet does not get a response back, it sends another keepalive packet after the net.ipv4.tcp_keepalive_intvl passes.
After enough keepalive packets are sent and no response is received, the sending device will assume the link is down, close the socket, and try to re-establish communications.
The number of keepalive packets sent before the device will reset if it does not get a response is configured in the net.ipv4.tcp_keepalive_probes parameter.

lsof

lsof Reference
lsof Reference II

The -i option without further qualification lists all open Internet socket files.
To refine the search, add network name, address, protocol name, service name or port number.

For example:

To know what process has a connection open to or from host my.server.com:
lsof -i@my.server.com

To limit results only to TCP (or UDP)/ specific port number / service name, you can add
those discriminators to the -i information:
lsof -iTCP@my.server.com:ftp-data

Connecting lsof with netstat

For example, this is the netstat output

Proto Recv-Q Send-Q Local Address Foreign Address (state)
tcp 0 0 vic.1023 ipscgate.login ESTABLISHED

What process is connected to service name login on ipscgate?

Option A. - Using service name.
Use lsof's -i option:

>lsof -iTCP@ipscgate:login
COMMAND PID USER FD TYPE DEVICE SIZE/OFF INODE NAME
rlogin 25023 abe 3u inet 0x10144168 0t184 TCP vic.cc:1023-> ipscgate.cc:login

Option B. - using PCB.
Use netstat -A option:

Notice the 0x10144168 in the DEVICE column of the lsof output.
That's the protocol control block (PCB) address.
Many netstat applications will display it with -A option:

netstat -A
PCB Proto Recv-Q Send-Q Local Address Foreign Address (state)
10144168 tcp 0 0 vic.1023 ipscgate.login ESTABLISHED

Now find this process using lsof:

lsof -i | grep 10144168
rlogin 25023 abe 3u inet 0x10144168 0t184 TCP vic.cc:1023-> ipscgate.cc:login

More lsof examples

List all network connections
lsof -i

COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
avahi-dae 515 avahi 13u IPv4 6848 0t0 UDP *:mdns
avahi-dae 515 avahi 16u IPv6 6851 0t0 UDP *:52060
cupsd 1075 root 5u IPv6 22512 0t0 TCP ip6-localhost:ipp (LISTEN)

List all network files in use by a specific process
lsof -i -a -p 234

You can also use the following
lsof -i -a -c ssh

The above command will list the network files opened by the processes starting with ssh.

List processes which are listening on a particular port
lsof -i :25

COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
exim4 2541 Debian-exim 3u IPv4 8677 TCP localhost:smtp (LISTEN)

List all TCP or UDP connections
lsof -i tcp;
lsof -i udp;

How to identify what is the process that is holding the port?

sudo lsof -i
sudo netstat -lptu
sudo netstat -tulpn

for example:

:~>% lsof -i | grep 43230

java 13927 user 171u IPv4 4074139617 0t0 TCP server-aps-1:43230->server-ora-1:proc (ESTABLISHED)

=============================
ifconfig
=============================

ifconfig is used to view the current network configuration

>% ifconfig 

eth0      Link encap:Ethernet  HWaddr 28:92:4A:2F:6F:90  

          inet addr:192.168.69.216  Bcast:192.168.69.255  Mask:255.255.255.192

          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

          RX packets:8387572303 errors:0 dropped:0 overruns:0 frame:0

          TX packets:8615008840 errors:0 dropped:0 overruns:0 carrier:0

          collisions:0 txqueuelen:1000 

          RX bytes:7334475993483 (6.6 TiB)  TX bytes:5923454851965 (5.3 TiB)

eth0:0    Link encap:Ethernet  HWaddr 28:92:4A:2F:6F:90  

          inet addr:192.168.69.231  Bcast:192.168.69.255  Mask:255.255.255.192

          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

eth0:1    Link encap:Ethernet  HWaddr 28:92:4A:2F:6F:90  

          inet addr:192.168.69.223  Bcast:192.168.69.255  Mask:255.255.255.192

          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

eth0:3    Link encap:Ethernet  HWaddr 28:92:4A:2F:6F:90  

          inet addr:192.168.69.229  Bcast:192.168.69.255  Mask:255.255.255.192

          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

eth0:5    Link encap:Ethernet  HWaddr 28:92:4A:2F:6F:90  

          inet addr:192.168.69.222  Bcast:192.168.69.255  Mask:255.255.255.192

          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

eth0:6    Link encap:Ethernet  HWaddr 28:92:4A:2F:6F:90  

          inet addr:192.168.69.206  Bcast:192.168.69.255  Mask:255.255.255.192

          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

eth2      Link encap:Ethernet  HWaddr 28:92:4A:2F:6F:94  

          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

          RX packets:34480079 errors:0 dropped:0 overruns:0 frame:0

          TX packets:34936034 errors:0 dropped:0 overruns:0 carrier:0

          collisions:0 txqueuelen:1000 

          RX bytes:2594272693 (2.4 GiB)  TX bytes:3063799522 (2.8 GiB)

eth3      Link encap:Ethernet  HWaddr 28:92:4A:2F:6F:96  

          inet addr:192.168.20.20  Bcast:192.168.20.127  Mask:255.255.255.128

          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

          RX packets:251475120 errors:0 dropped:0 overruns:0 frame:0

          TX packets:34910610 errors:0 dropped:0 overruns:0 carrier:0

          collisions:0 txqueuelen:1000 

          RX bytes:249823838895 (232.6 GiB)  TX bytes:3060739778 (2.8 GiB)

lo        Link encap:Local Loopback  

          inet addr:127.0.0.1  Mask:255.0.0.0

          UP LOOPBACK RUNNING  MTU:16436  Metric:1

          RX packets:1861721437 errors:0 dropped:0 overruns:0 frame:0

          TX packets:1861721437 errors:0 dropped:0 overruns:0 carrier:0

          collisions:0 txqueuelen:0 

          RX bytes:1339967244643 (1.2 TiB)  TX bytes:1339967244643 (1.2 TiB)

=============================

tcpdump

=============================

Useful Options

-A Print each packet (minus its link level header) in ASCII

-C count Exit after receiving count packets.

-d Dump the compiled packet-matching code in a human readable form to standard output and stop.

-i By default, all the packets flowing through all the interfaces would be captured. With -i option only traffic from particular ethernet interface.would be captured.
 tcpdump -i eth1

-l  Make stdout line buffered. 

  Useful if you want to see the data while capturing it.

  For Example: tcpdump -l | tee dat or tcpdump -l > dat & tail -f dat

-n Leave the IP address. 

     Don't convert addresses (i.e., host addresses, port numbers, etc.) to names.

-O --no-optimize Do not run the packet-matching code optimizer. 

    This is useful only if you suspect a bug in the optimizer.

-Q Quick (quiet?) output. Print less protocol information so output lines are shorter.

-v, -vv, -vvv When parsing and printing, produce more (and more) verbose output.

-w - Write output to a file

Examples:

tcpdump host some_host

To print all packets arriving at or departing from some_host

tcpdump host some_host and \( hostA or hostB \)

To print traffic between some_host and either hostA or hostB

tcpdump ip host my_host and not hostA

To print all IP packets between my_host and any host except hostA

tcpdump net ucb-ether

To print all traffic between local hosts and hosts at ucb-ether network

tcpdump -i eth0

With -i option you can specify the particular ethernet interface traffic to capture.

Without -c tcpdump would captute packets until you cancel the tcpdump command. 

tcpdump -c 2 -i eth0

With -c option you can specify the number of packets to capture.

Without -c tcpdump would captute packets until you cancel the tcpdump command. 

tcpdump -w 08232010.pcap -i eth0
Write output to a file 08232010.pcap.

tcpdump -n -i eth0
Captures the packets and it  display the IP address, without conversion to DNS.

tcpdump -n -tttt -i eth0

Capture packets with readable timestamp

tcpdump -w g_1024.pcap greater 1024

Read packets longer than 1024 bytes and log data to file g_1024.pcap

tcpdump -w g_1024.pcap less 1024

Read packets less than 1024 bytes and log data to file g_1024.pcap

tcpdump -i eth0 <protocol>, for example $ tcpdump -i eth0 arp

Receive only the packets of a specific protocol type

Protocol options: fddi, tr, wlan, ip, ip6, arp, rarp, decnet, tcp and udp. 

tcpdump -i eth0 port 22

Receive packets flows on a particular port 

tcpdump -v or tcpdump -vv or tcpdump -vvv

Receive verbose output

tcpdump -w xpackets.pcap -i eth0 dst 10.181.140.216 and port 22

Receive packets with destination IP 10.181.140.216 and port 22

tcpdump -w comm.pcap -i eth0 src xxx.xxx.xxx.001 and port 22 and dst xxx.xxx.xxx.002 and port 22

Captures all ssh packets flowing between the source and destination addresses.

File comm.pcap can be analyzed using any network protocol analyzer tool.

=============================

mii-show

=============================

mii-show is used to see current open networks status.

>% mii-show

Detected 4 Interfaces

eth0 is { elink=yes speed=100Mb autoneg=on name=eth0 duplex=Full }

eth1 is { elink=no speed=Unknown autoneg=on name=eth1 duplex=Half }

eth2 is { elink=yes speed=100Mb autoneg=on name=eth2 duplex=Full }

eth3 is { elink=yes speed=100Mb autoneg=on name=eth3 duplex=Full }

=============================
MTU and Packet size
=============================
MTU: Maximum Transmission Unit
The default size for Packet size is 1400 bytes.

How to set the correct MTU size (Linksys Reference)
ping [url / local server or IP address] –f –l xxxx
Where xxxx is the packet size (value) which you will test.
For example:
>ping 10.16.39.122 -f -l 1400

Pinging 10.16.39.122 with 1400 bytes of data:

Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.

Ping statistics for 10.16.39.122:

Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),

Here are the results that you may get after doing the ping test:

• Four (4) replies received: This means that the packet size entered is either within or the actual MTU size used within your network.

• Destination net unreachable: This means that there was no path or route to the destination or the address.

• Request Timed Out: This means that within the default wait time period (1 second), there was no response.

• Packet needs to be fragmented but DF set: This means that the packet size you entered is too high for your MTU value.

• Bad parameter –f: This means that you have typed the command incorrectly.

Handle case for Packet needs to be fragmented but DF set

Try with packet size of 1248:

>ping 10.16.39.122 -f -l 1248

Pinging 10.16.39.122 with 1248 bytes of data:

Reply from 10.16.39.122: bytes=1248 time=312ms TTL=58

Reply from 10.16.39.122: bytes=1248 time=338ms TTL=58

Reply from 10.16.39.122: bytes=1248 time=339ms TTL=58

Ping statistics for 10.16.39.122:

Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),

Approximate round trip times in milli-seconds:

Minimum = 312ms, Maximum = 339ms, Average = 325ms

The -l flag would set the MTU size in current cmd window.

To change the settings in general, need to access the Router, and per server enter MTU value..

=============================

ORA-03113 and MTU

=============================

To see the current MTU settings:

netsh interface ip show interface

The pre-requirement is to have netsh service running.

=============================

ORA-03113 and MTU

=============================

ORA-03113: end-of-file on communication channel.

Consider this common scenario: Oracle Client and Oracle Server communicate via Network.

It may happen the MTU on the Client router is set to too high value.

In this case, the client requests from the remote database are not received back, and error ORA-03113 is thrown:

The solution would be to lower the MTU to the default value of 1400, or even lower.

Oracle DBA by Example. Code samples, Scripts, Reference.

Pages

Thursday, March 27, 2014

Common Network Issues. netstat, lsof, tracert, tcpdump