resolved – VPN Service not available, The VPN agent service is not responding. Please restart this application after a while.

March 30th, 2015

Today when I tried to connect to VPN through Cisco AnyConnect Secure Mobility Client, the following error dialog prompted:

 

VPN Service not available

VPN Service not available

And after I clicked "OK" button, the following dialog prompted:

The VPN agent service is not responding

The VPN agent service is not responding

So all of the two dialogs were complaining about "VPN service" not available/not responding. So I ran "services.msc" in windows run and found below:

vpn service

vpn service

When I checked, the service "Cisco AnyConnect Secure Mobility Agent" was stopped, and the "Startup type" was "Manual". So I changed "Startup type" to "Automatic", click "Start", then "OK" to save.

After this, Cisco AnyConnect Secure Mobility Client was running ok and I can connect through it to VPN.

resolved – ORA-01013: user requested cancel of current operation

March 24th, 2015

ORA-01013: user requested cancel of current operation may occur in the following occasions:

  • All events blocking the shutdown do not occur within one hour, the shutdown operation aborts with the following message: ORA-01013: user requested cancel of current operation.
  • This message is also displayed if you interrupt the shutdown process, for example by pressing CTRL-C.
Categories: Databases, IT Architecture, Oracle DB Tags:

resolved – ext3: No journal on filesystem on disk

March 23rd, 2015

Today I met below error when trying to mount a disk:

[root@testvm ~]# mount /scratch
mount: wrong fs type, bad option, bad superblock on /dev/xvdb1,
missing codepage or other error
In some cases useful info is found in syslog - try
dmesg | tail or so

First I ran fsck -y /dev/xvdb1, but after it's done, the issue was still there(sometimes fsck -y /dev/xvdb1 could resolve this though). So as it suggested, I ran a dmesg | tail:

[root@testvm scratch]# dmesg | tail
Installing knfsd (copyright (C) 1996 okir@monad.swb.de).
NFSD: Using /var/lib/nfs/v4recovery as the NFSv4 state recovery directory
NFSD: starting 90-second grace period
ext3: No journal on filesystem on xvdb1
ext3: No journal on filesystem on xvdb1
ext3: No journal on filesystem on xvdb1
ext3: No journal on filesystem on xvdb1

So from here we can see that the root cause for mounting failure was "ext3: No journal on filesystem on xvdb1". I first ran "fsck -y /dev/xvdb1", and try mount again. But the issue was still there. So I tried with adding ext3 journal on that disk:

[root@testvm qgomsdc1]# tune2fs -j /dev/xvdb1
tune2fs 1.39 (29-May-2006)
Creating journal inode:

done
This filesystem will be automatically checked every 20 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.

After this, the mount succeeded.

Categories: IT Architecture, Kernel, Linux, Systems, Unix Tags:

resolved – ORA-00020: maximum number of processes (1000) exceeded

March 18th, 2015

Today I encountered ORA-12516 error when trying to access oracle database:

[root@client-doxer ~]# sqlplus tauser/password1@rac0102-r.example.com:1521/qainfac1

SQL*Plus: Release 11.2.0.3.0 Production on Tue Mar 17 07:31:04 2015

Copyright (c) 1982, 2011, Oracle. All rights reserved.

ERROR:
ORA-12516: TNS:listener could not find available handler with matching protocol
stack

Enter user-name:

Then I had a try of connecting using VIP instead of scan name, but it failed too:

[root@client-doxer ~]# sqlplus tauser/password1@rac0102-v.example.com:1521/qainfac1

SQL*Plus: Release 11.2.0.3.0 Production on Tue Mar 17 07:37:22 2015

Copyright (c) 1982, 2011, Oracle. All rights reserved.

ERROR:
ORA-12516: TNS:listener could not find available handler with matching protocol
stack

Enter user-name:

Then on the database server, I had a check of service qainfac1:

[root@rac01 crsd]# /u01/app/11.2.0.4/grid/bin/crsctl status res -t|grep -A5 ora.qainf1.db
ora.qainf1.db
1 ONLINE ONLINE rac01 Open
2 OFFLINE OFFLINE Instance Shutdown
ora.qainf1.qainfac1.svc
1 ONLINE ONLINE rac01
2 OFFLINE OFFLINE

So one instance is running fine. I tried sqlplus connection from local server:

[oracle@rac01 ~]$ sqlplus / as sysdba

SQL*Plus: Release 11.2.0.4.0 Production on Tue Mar 17 07:45:39 2015

Copyright (c) 1982, 2013, Oracle. All rights reserved.

ERROR:
ORA-00020: maximum number of processes (1000) exceeded

Enter user-name: ^C

That's it, "ORA-00020: maximum number of processes (1000) exceeded". Then it's going to be a question of adjusting parameter PROCESSES. As parameter PROCESSES cannot be changed with ALTER SYSTEM unless a server parameter file was used to start the instance and the change takes effect in subsequent instances, so a bounce of instance is needed to activiate the new setting:

SQL> set lines 200
SQL> col NAME for a30
SQL> col VALUE for a40
SQL> select NAME,VALUE,ISSES_MODIFIABLE,ISSYS_MODIFIABLE,ISINSTANCE_MODIFIABLE from v$parameter where name='processes';
NAME VALUE ISSES ISSYS_MOD ISINS
------------------------------ ---------------------------------------- ----- --------- -----
processes 1500 FALSE FALSE FALSE

SQL> show parameter processes;

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
aq_tm_processes integer 1
db_writer_processes integer 3
gcs_server_processes integer 2
global_txn_processes integer 1
job_queue_processes integer 1000
log_archive_max_processes integer 4
processes integer 1000

In trace file /u01/app/oracle/diag/rdbms/qainf1/qainf12/trace/alert_qainf12.log, I can see below errors:

Unable to allocate flashback log of 51094 blocks from
current recovery area of size 214748364800 bytes.
Recovery Writer (RVWR) is stuck until more space
is available in the recovery area.
Unable to write Flashback database log data because the
recovery area is full, presence of a guaranteed
restore point and no reusable flashback logs.

Here's Fast Recovery Area info:

SQL> show parameter db_recovery_file_dest;

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
db_recovery_file_dest string +DATA
db_recovery_file_dest_size big integer 200G

And here's ASM diskgroup info:

[oracle@rac01 ~]$ export ORACLE_SID=+ASM2
[oracle@rac01 ~]$ export ORACLE_HOME=/u01/app/11.2.0.4/grid
[oracle@rac01 ~]$ export PATH=$ORACLE_HOME/bin:$PATH
[oracle@rac01 ~]$ sqlplus / as sysasm

SQL*Plus: Release 11.2.0.4.0 Production on Wed Mar 18 02:27:13 2015

Copyright (c) 1982, 2013, Oracle. All rights reserved.

Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
With the Real Application Clusters and Automatic Storage Management options

SQL> set lines 200;
SQL> select name, total_mb, free_mb, total_mb-free_mb used_mb from v$asm_diskgroup;

NAME TOTAL_MB FREE_MB USED_MB
------------------------------ ---------- ---------- ----------
DATA 4681689 533392 4148297

I had a check of restore points:

SQL> col NAME for a20
SQL> col time for a40
SQL> col SCN for 999999999999999
SQL> col STORAGE_SIZE for 999999999999999
SQL> SELECT NAME, SCN, TIME, DATABASE_INCARNATION#, GUARANTEE_FLASHBACK_DATABASE,STORAGE_SIZE FROM V$RESTORE_POINT;

NAME SCN TIME DATABASE_INCARNATION# GUA STORAGE_SIZE
-------------------- -------------- ---------------------------------------- --------------------- --- ------------
GRPT_BF_UPGR 14035000000000 03-MAR-15 04.16.12.000000000 PM 2 YES 214310000000

And I dropped the restore point to free space it's no longer needed to keep the restore point:

SQL> drop restore point GRPT_BF_UPGR;

After this, 214G space released from FRA and I can startup DB then set processes parameter to 1500(kill some processes with root by "ps -ef|grep <sid>" if sqlplus won't work even on local server):

SQL> alter system set processes=1500 scope=spfile;
SQL> shutdown immediate;
SQL> startup mount;
SQL> alter database flashback on;
SQL> alter database open;
SQL> select LOG_MODE,flashback_on from v$database;
LOG_MODE FLASHBACK_ON
------------ ------------------
ARCHIVELOG NO

Categories: Databases, IT Architecture, Oracle DB Tags:

sendmail DSN: Data format error

March 5th, 2015

If you met error when sending mail using sendmail(or linux mail/mailx command), then you should check /var/log/maillog for details. For example:

Mar 5 02:39:10 testhost1 sendmail[15281]: t252dAZr015281: from=root, size=78, class=0, nrcpts=1, msgid=<201503050239.t252dAZr015281@testhost1.us.example.com>, relay=root@localhost
Mar 5 02:39:10 testhost1 sendmail[15282]: t252dA8Z015282: from=<root@testhost1.us.example.com>, size=393, class=0, nrcpts=1, msgid=<201503050239.t252dAZr015281@testhost1.us.example.com>, proto=ESMTP, daemon=MTA, relay=localhost.localdomain [127.0.0.1]
Mar 5 02:39:10 testhost1 sendmail[15281]: t252dAZr015281: to=user1@example.com, ctladdr=root (0/0), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=30078, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (t252dA8Z015282 Message accepted for delivery)
Mar 5 02:39:10 testhost1 sendmail[15284]: t252dA8Z015282: to=<user1@example.com>, ctladdr=<root@testhost1.us.example.com> (0/0), delay=00:00:00, xdelay=00:00:00, mailer=esmtp, pri=120393, relay=smtpserver1.example.com. [192.151.231.4], dsn=5.6.0, stat=Data format error
Mar 5 02:39:10 testhost1 sendmail[15284]: t252dA8Z015282: t252dA8Z015284: DSN: Data format error
Mar 5 02:39:10 testhost1 sendmail[15284]: t252dA8Z015284: to=<root@testhost1.us.example.com>, delay=00:00:00, xdelay=00:00:00, mailer=local, pri=31660, dsn=2.0.0, stat=Sent

From here, you can see that after relaying, the mail finally failed with DSN code 5.6.0(Delivery Status Notification extension of SMTP). So you should check the code details:

5 Permanent or Fatal error. This can be caused by a non existent email address, DNS problem, or your email was blocked by the receiving server.
X.6.0 - Other or undefined media error

X.6.0 Other or undefined media error Not given Something about the content of a message caused it to be considered undeliverable and the problem cannot be well expressed with any of the other provided detail codes.

PS:

For more info abotu DSN code, you can check http://www.inmotionhosting.com/support/email/email-troubleshooting/smtp-and-esmtp-error-code-list or http://tools.ietf.org/rfc/rfc3463.txt or http://www.iana.org/assignments/smtp-enhanced-status-codes/smtp-enhanced-status-codes.xml for details.

Categories: IT Architecture, Linux, Systems Tags:

TCP Window Scaling – values about TCP buffer size

February 4th, 2015

TCP Window Scaling(TCP socket buffer size, TCP window size)

/proc/sys/net/ipv4/tcp_window_scaling
/proc/sys/net/ipv4/tcp_rmem - memory reserved for TCP rcv buffers. minimum, initial and maximum buffer size
/proc/sys/net/ipv4/tcp_wmem - memory reserved for TCP snd buffers
/proc/sys/net/core/rmem_max - maximum receive window
/proc/sys/net/core/wmem_max - maximum send window

The following values (which are the defaults for 2.6.17 with more than 1 GByte of memory) would be reasonable for all paths with a 4MB BDP or smaller:

echo 1 > /proc/sys/net/ipv4/tcp_moderate_rcvbuf #autotuning enabled. The receiver buffer size (and TCP window size) is dynamically updated (autotuned) for each connection. (Sender side autotuning has been present and unconditionally enabled for many years now).
echo 108544 > /proc/sys/net/core/wmem_max
echo 108544 > /proc/sys/net/core/rmem_max
echo "4096 87380 4194304" > /proc/sys/net/ipv4/tcp_rmem
echo "4096 16384 4194304" > /proc/sys/net/ipv4/tcp_wmem

Advanced TCP features

cat /proc/sys/net/ipv4/tcp_timestamps
cat /proc/sys/net/ipv4/tcp_window_scaling
cat /proc/sys/net/ipv4/tcp_sack

Here are some background knowledge:

  • The throughput of a communication is limited by two windows: the congestion window and the receive window. The former tries not to exceed the capacity of the network (congestion control) and the latter tries not to exceed the capacity of the receiver to process data (flow control). The receiver may be overwhelmed by data if for example it is very busy (such as a Web server). Each TCP segment contains the current value of the receive window. If for example a sender receives an ack which acknowledges byte 4000 and specifies a receive window of 10000 (bytes), the sender will not send packets after byte 14000, even if the congestion window allows it.
  • TCP uses what is called the "congestion window", or CWND, to determine how many packets can be sent at one time. The larger the congestion window size, the higher the throughput. The TCP "slow start" and "congestion avoidance" algorithms determine the size of the congestion window. The maximum congestion window is related to the amount of buffer space that the kernel allocates for each socket. For each socket, there is a default value for the buffer size, which can be changed by the program using a system library call just before opening the socket. There is also a kernel enforced maximum buffer size. The buffer size can be adjusted for both the send and receive ends of the socket.
  • To get maximal throughput it is critical to use optimal TCP send and receive socket buffer sizes for the link you are using. If the buffers are too small, the TCP congestion window will never fully open up. If the receiver buffers are too large, TCP flow control breaks and the sender can overrun the receiver, which will cause the TCP window to shut down. This is likely to happen if the sending host is faster than the receiving host. Overly large windows on the sending side is not usually a problem as long as you have excess memory; note that every TCP socket has the potential to request this amount of memory even for short connections, making it easy to exhaust system resources.
  • More about TCP Buffer Sizing is here.
  • More about /proc/sys/net/ipv4/* Variables is here.