Flush the DNS cache

How do i flush the DNS cache on an iPhone?

TrYaN73 wrote:
How do i flush the DNS cache on an iPhone?
There's no specific way to do that exact thing in iOS. However, resetting network settings will help resolve a lot of network-related issues for both Wi-Fi and cellular connections.
Reset network settings by tapping Settings > General > Reset > Reset Network Settings.

Similar Messages

Flushing the DNS cache

I'm having trouble with a Web site when I access it on my home computer, yet this same site looks fine on my Mini at work. One section of the index page generates a "can't find server" error, and the site's own logo won't display properly. It is a free hosting site. Sometimes I can upload files to it, other times I get a can't-find-server error when I try.
In answer to my query about this (to which I helpfully attached a screenshot of the incompletely loaded index page and its error messages), the host is telling me that I should "flush my DNS cache," which they say involves going into Terminal and giving the command "ookupd -flushcache" [sic]. (I've already surfed this briefly and the first result confirmed my suspicion that this doofus hasn't mastered copy-and-paste technique and the command actually should be "lookupd- flushcache".)
It's not just that their site doesn't load fully, though. They have some stuff on one of their pages that they encourage users to hotlink on personal Web sites, and I have done that with one of their banners. The banner, which was fine for months, now appears on my page as a broken icon, too, although it, like the site's home page, loads fine on my computer at work.
My first question is, is there any harm in flushing the DNS cache? The OS Daily page where I think they copied this advice from makes it sound like this is something only a Web server would need. If I do it on my home machine, could it cause problems? Could it disable my Internet connectivity?
Second, less urgent question, more for the netgeeks out there: Do you think this is a likely solution to my problem? Especially considering that the problem involves not only their site but an element on an external site linking back to them? I hate to play the sucker for some low-level geek whose main mission is to deflect my query.
Thanks
Kathi

Kathi--
Like BDAqua says, there's nothing to worry about flushing the DNS cache. It's true that most people probably don't need to do it very often, but it's something easy and harmless to try, and it might well fix problems like yours.
One handy feature of Safari, even if you don't use it for anything else, is the "Activity" window. Open it from the "View" menu, and watch as your page loads. You can see exactly which components on the page are loading, which aren't and where they should be coming from. If you double-click an element in that list, Safari will try to open it in a new window. That is sometimes enough to give a clue as to why something isn't working.
You can use Safari's activity list along with the Network Utility from your Utilities folder to try to figure out why you're not getting the page elements. Suppose a graphic is listed as coming from http://www.server1.com/images/logo.jpg, but it's not loading.
First thing I would try in the Network Utility is to see if it will respond to pings. From that example, enter "www.server1.com" on the "Ping" page of the Network Utility and see if it answers back.
To find out if it's a DNS problem, you can use Safari's list to get the addresses of the problem elements, then see if the IP addresses match up on your computer at home to the one at work. If they don't, then it could be stale DNS.
You can use the Network Utility for DNS lookups, but I think they're hard to read, and, since you're already thinking about using the Terminal to flush the DNS cache, you can use nslookup. It's really simple:
<pre class="command">nslookup www.apple.com</pre>
Will give you something like this (the first two lines will likely be different):
Server: 208.67.222.222
Address: 208.67.222.222#53
Non-authoritative answer:
www.apple.com canonical name = www.apple.com.akadns.net.
Name: www.apple.com.akadns.net
Address: 17.251.200.32
If the addresses don't match, or you get a message that it can't find anything for your server, then you know it's a DNS problem. Perhaps they've changed some addresses and your home ISP's DNS servers themselves aren't updating.
You can even use nslookup to see what different DNS servers say about an address. Just add the IP address of a DNS server after the address you want to look up:
<pre class="command">nslookup www.apple.com 208.67.220.220</pre>
Just do a search on the 'net for free DNS servers, and you'll find a bunch to choose from.
charlie

How do I flush the dns?

My laptop is running really slow. I have done all of the normal stuff like deleting internet temep & the cache. I was told that "Flushing the DNS" could help me but my Son only has pc's so didn't know how to do it on a Mac.
Any help would be appreciated!
Thank you in advance! ~Laurie

Cache and temp files exist to increase performance and should not require manual deletion.
The first thing to do is ensure you have adequate backups, because what you describe can be a symptom of impending disk failure.
To help determine the possible causes of this behaviour read the following. None of what follows is intended to fix anything, but it will provide the additional information required to advance troubleshooting. There are four separate parts to it; read everything first.
Boot OS X Recovery by holding ⌘ and r (two fingers) while you start your Mac. At the Mac OS X Utilities screen, select Disk Utility. Select your startup volume (usually named "Macintosh HD") and click the Repair Disk button. Describe any errors it reports in red. If Disk Utility reports "The volume Macintosh HD appears to be OK" in green then you can be reasonably (though not completely) assured your hard disk is in good working order.
When it finishes restart your Mac and test again for operation. If it's still not behaving as you expect it should, please post the results of EtreCheck in accordance with the following instructions:
Apple Support Communities contributor etresoft wrote a very useful app to quickly gather certain system information that may help point to a cause of this problem. Read about it here. It contains a link to download EtreCheck. Don't download it from anywhere else (such as may be found by following the results of an Internet search).
Click Open - etresoft contributes to this forum frequently and can be considered a trustworthy developer.
It will take a moment to run as it collects its data.
Copy and paste its output in a reply.
Do not be concerned about anything that says "Problem" or “failed” or anything else that may appear in red.
EtreCheck was designed to remove any personal information (such as your computer's name and serial numbers) but if you see anything that looks like an email address or any other personal information that should not be divulged to others, please delete or obscure that information when you post the reply.
When you are finished with EtreCheck, quit the program. It occupies very little space, and you can keep it or drag it to the Trash as you wish.
After completing the above please determine if the problems also occur in "Safe Mode":
Safe Mode or "Safe Boot" is a troubleshooting mode that bypasses all third party system extensions and loads only required system components. Read about it: Starting up in Safe Mode
You must disable FileVault before you can start your Mac in Safe Mode.
Starting your Mac in Safe Mode will take longer than usual, graphics will not render smoothly, audio is disabled on some Macs, and some programs (iTunes for example) may not work at all.
Merely starting your Mac in Safe Mode is not intended to resolve the problem, it's to observe its performance without certain additional components.
To end Safe Mode restart your Mac normally. Shutdown will take longer as well.
System performance problems for reasons that cannot be isolated to any other cause justify an SMC reset. Be sure to read the procedure carefully and follow all the steps exactly as written, even if they seem inapplicable or trivial.

HT5343 Resetting the DNS cache does not seem to work on OS X 10.8, what does really work?

Resetting the DNS cache does not seem to work on OS X 10.8, what does really work?
Desired activity: access a site that used to not have a SSL connection through the new https:// root domain. I can accomplish the task over a machine running Windows 7 or XP but flushing the dns of my mac does not affect the outcome — I am still redirected to the hosting provider's website whenever I tried to access the domain with a https:// prefix rather than http://
I tried sudo killall -HUP mDNSResponder and it's older alternative but no luck.

In the terminal:
dscacheutil -flushcache
and to get a very detailed report on the state of your DNS cache in /var/logs/system.log:
sudo killall -INFO mDNSResponder

How do I flush my DNS cache

My internet lookup is slow. I have read that I can fix this by using either openDNS or googleDNS servers. How Do I flush my DNS cache after switching DNS servers?

Restart the computer.

10G NEW FEATURE-HOW TO FLUSH THE BUFFER CACHE

제품 : ORACLE SERVER
작성날짜 : 2004-05-25
10G NEW FEATURE-HOW TO FLUSH THE BUFFER CACHE
===============================================
PURPOSE
이 자료는 Oracle 10g new feature 로 manual 하게
buffer cache 를 flush 할 수 있는 기능에 대하여 알아보도록 한다.
Explanation
Oracle 10g 에서 new feature 로 소개된 내용으로 SGA 내 buffer cache 의
모든 data 를 command 수행으로 clear 할 수 있다.
이 작업을 위해서는 "alter system" privileges 가 있어야 한다.
Buffer cache flush 를 위한 command 는 다음과 같다.
주의) 이 작업은 database performance 에 영향을 줄 수 있으므로 주의하여 사용하여야 한다.
SQL > alter system flush buffer_cache;
Example
x$bh 를 query 하여 buffer cache 내 존재하는 정보를 확인한다.
x$bh view 는 buffer cache headers 정보를 확인할 수 있는 view 이다.
우선 test 로 table 을 생성하고 insert 를 수행하고
x$bh 에서 barfil column(Relative file number of block) 과 file# 를 조회한다.
1) Test table 생성
SQL> Create table Test_buffer (a number)
2 tablespace USERS;
Table created.
2) Test table 에 insert
SQL> begin
2 for i in 1..1000
3 loop
4 insert into test_buffer values (i);
5 end loop;
6 commit;
7 end;
8 /
PL/SQL procedure successfully completed.
3) Object_id 확인
SQL> select OBJECT_id from dba_objects
2 where object_name='TEST_BUFFER';
OBJECT_ID
42817
4) x$bh 에서 buffer cache 내에 올라와 있는 DBARFIL(file number of block) 를 조회한다.
SQL> select ts#,file#,dbarfil,dbablk,class,state,mode_held,obj
2 from x$bh where obj= 42817;
TS# FILE# DBARFIL DBABLK CLASS STATE MODE_HELD J
9 23 23 1297 8 1 0 7
9 23 23 1298 9 1 0 7
9 23 23 1299 4 1 0 7
9 23 23 1300 1 1 0 7
9 23 23 1301 1 1 0 7
9 23 23 1302 1 1 0 7
9 23 23 1303 1 1 0 7
9 23 23 1304 1 1 0 7
8 rows selected.
5) 다음과 같이 buffer cache 를 flush 하고 위 query 를 재수행한다.
SQL > alter system flush buffer_cache ;
SQL> select ts#,file#,dbarfil,dbablk,class,state,mode_held,obj
2 from x$bh where obj= 42817;
6) x$bh 에서 state column 이 0 인지 확인한다.
0 은 free buffer 를 의미한다. flush 이후에 state 가 0 인지 확인함으로써
flushing 이 command 를 통해 manual 하게 수행되었음을 확인할 수 있다.
Reference Documents
<NOTE. 251326.1>

I am also having the same issue. Can this be addressed or does BEA provide 'almost'
working code for the bargin price of $80k/cpu?
"Prashanth " <[email protected]> wrote:
>
Hi ALL,
I am using wl:cache tag for caching purpose. My reqmnt is such that I
have to
flush the cache based on user activity.
I have tried all the combinations, but could not achieve the desired
result.
Can somebody guide me on how can we flush the cache??
TIA, Prashanth Bhat.

How do you flush the negative cache?

Hi all,
I am working with NetWeaver 2004s SR3 SP14 on SuSE 10 with Oracle. I wrote a custom login module and was trying to get SAP to load it. At first I made some reference mistakes (in provider.xml under the references tab) and it wouldn't load. Then I fixed the reference errors and tried to get it to load again and it still wouldn't load. I just keep on getting the error message:
[EXCEPTION]
{1}#2#com.mycompany.dc.netweaver.MyLoginModule#java.lang.ClassNotFoundException:
com.mycompany.dc.netweaver.MyLoginModule
Found in negative cache
I shut down and restarted SAP several times (using stopsap and startsap) and undeploying and redeploying my login module (the fixed version), but still, SAP refuses to load my login module because it is in the "negative cache".
If I keep the code the same, but change the name of the Java class and component name in provider.xml, then SAP happily loads my login module.
So I can work around the issue, but it is really annoying to change your configuration every time you make a mistake with the references... So I was hoping that someone would know how to flush the negative cache. Do I have to go into the database to do it?
-- Katrina

Hi Katrina,
did you found a way to flush the chache?
kind Regards,
Gerardo J

How can I clear the DNS cache?

I haven't been able to connect to my local Library since January. When I key in the URL, it starts the access routine and then after about 20 minutes, I have to kill it because nothing happens. I contacted the IT folks at the library and was told that they had made a few changes around the time my problem began so maybe the DNS cache was still pointing at the old info. He recommended that I enter TERMINAL mode and try to clear the DNS cache, using "sudo dscacheutil -flushcache" command. . I attempted this several times, even changing my applid password, and kept getting invalid responses.

I did try that and after a few trys it finally worked. It took quite awhile for the window for the library to finally come up, but it did and I am now able to get in and out with no problems with my library access. Now when I call up my bank, parts of it don't come up and it kicks me out. Now, I'll have to search for what fixes that - as it has happened before, so I know it's fixable. Thanks for you help though.

HT203163 I cannot access iTunes store from my laptop. I could for years but suddenly - no. Have removed all recently installed software. Have uninstalled and re-installed both my anti-virus software and iTunes. Have allowed pop-ups. Have flushed the DNS.

I cannot access iTunes store from my laptop. I could for years but suddenly - no.
Have removed all recently installed software. Have uninstalled and re-installed both my anti-virus software and iTunes.
Have allowed pop-ups.
Have flushed the DNS. Nothing.
Still can't access the store. Please help!

Close your iTunes,
Go to command Prompt -
(Win 7/Vista) - START/ALL PROGRAMS/ACCESSORIES, right mouse click "Command Prompt", choose "Run as Administrator".
(Win XP SP2 n above) - START/ALL PROGRAMS/ACCESSORIES/Command Prompt
In the "Command Prompt" screen, type in
netsh winsock reset
Hit "ENTER" key
Restart your computer.
If you do get a prompt after restart windows to remap LSP, just click NO.
Now launch your iTunes and see if it is working now.
If you are still having these type of problems after trying the winsock reset, refer to this article to identify which software in your system is inserting LSP:
iTunes 10.5 for Windows: May see performance issues and blank iTunes Store
http://support.apple.com/kb/TS4123?viewlocale=en_US

Mail and the DNS Cache

My web server name has recently changed. I ran "lookupd -flushcache" to flush my local cache and I was able to reach my website using the domain name within minutes of the change.
Mail has however not been able to find the server. After a day or two I placed my mail into a backup folder and recreated the account and it works fine.
My questions are:
1. Does Apple Mail use its own cache? I know thats not the case with other operating systems and didn't think it was with OSX until I had this problem.
2. If so would clearing the preferences for mail fix this? Would there be an alternate way to prevent loosing all of the other preferences.
Best Regards,
Justin

Hi Justin, and a warm welcome to the forums!
Not certain, but this can fix myriad Mail problems, without destroying Prefs...
Safe Boot from the HD, (holding Shift key down at bootup), it will try to repair your Disk Directory while the spinning radian is happening, so let it go, run Disk Utility in Applications>Utilities, then highlight your drive, click on Repair Permissions, then move these folder & file to the Desktop.
Move this Folder to the Desktop...
/Users/YourUserName/Library/Caches/Mail/
Move this file to the Desktop...
/Users/YourUserName/Library/Mail/Envelope Index
Reboot.

How do I flush the portlet cache?

I have tried using the portlet cache (renderCacheable="true" ) on some data intensive pages and its working fine. When i make changes to to the data i need to be able to flush that cache though so that the portlets show the updated data.
I have tried to find a way to do this programaticly but so far i havent found any solution. How do i do this?

Create a backingFile on the portlet
and from one of the methods (say handlePostbackData)
call
PortletBackingContext.getBackingContext(request).invalidateCache();
Chris Jolley
Portal Architect

Flushing the Servlet Cache or buffer(maybe) ^o^

Hi,
I wrote a few JSPs that use servlets and scriplets using import and include attributes to extract data from a database table. Everything works fine, except when I refresh the page the results are shown multiple times.
That is to say, the servlets seem to remember the previously generated values from the table and calculations, and displays it before showing the new results. I tried using the flush="true" attribute, but to no avail. After about 10 mins or if i restart Tomcat the servlets would clear the cache.
I am writing these JSp for a school assignment, and so far this is the part that I am having trouble dealing with. Is there a workaround for this? or is this an implementation error in my part? Any help would be appreciated. Thanks in advance!
Cheers,
-Shawn

Well thats interesting. I wrote a test Servlet program to see the newsbean output and I get the same problem now and It appends the old result. I realize that the trouble is not in the include statement, rather in the servlet itself.
I looked over the code to see what it could be, but couldn't catch it. But maybe you might see something different. So I will include the code for the TestServlet and the dependat classes. And Philip I appreciate your effort trying to help me out with this! : )
test Servlet class
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.ListIterator;
import java.sql.*;
public class NewsServlet
extends HttpServlet {
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
NewsBean NewsPiece = null;
try
staffMembers = new NewsBean();
catch (SQLException ex)
//iterating through news list
ListIterator li = null;
try
li = NewsPiece.getNewsItem().listIterator();
catch (SQLException ex1)
String myNews="";
while(li.hasNext()){
NewsItem news = (NewsItem) li.next();
myNews += news.getTitle()+" \t"
news.getDescription()" \t"
+ news.getSubmitdate() +" \t"
news.getEndDate()" \t"
news.getAuthor()"<p>";
String docType =
"<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.0 " +
"Transitional//EN\">\n";
out.println(docType +
"<HTML>\n" +
"<HEAD><TITLE>News</TITLE></HEAD>\n" +
"<BODY BGCOLOR=\"#FDF5E6\">\n" +
"<H1>News</H1>\n" +
myNews+
"</BODY></HTML>");
This is the newsbean class
import package.name.sqlAdapter; //This is used to simplify database connections
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.LinkedList;
public class NewsBean{
private static ResultSet results;
private static LinkedList newsItems = new LinkedList();
public NewsBean() throws SQLException{
//connect to DB
sqlAdapter sqlConnection = new sqlAdapter();
//Get Staff list
String query = "SELECT * FROM `news` ";
results = (ResultSet) sqlConnection.runCustomQuery(query);
public LinkedList getNewsItem()throws SQLException{
while(results.next()) {
//read in columns
String description = results.getString("description");
String title = results.getString("title");
String submitDate = results.getString("submit_date");
String endDate = results.getString("end_date");
//String author = results.getString("author");
String picture = results.getString("picture");
String id = results.getString("id");
//create NewsItem object and add to list
NewsItem news = new NewsItem(title, description, submitDate, endDate, picture, id);
newsItems.add(news);
return newsItems;
Here is the NewsItem Class
public class NewsItem
private String title;
private String description;
private String submitDate;
private String endDate;
private String author;
private String picture;
private String id;
public NewsItem(String Title, String Description, String SubmitDate, String EndDate,String Picture, String ID){
this.title = Title;
this.description = Description;
this.submitDate = SubmitDate;
this.endDate = EndDate;
//this.author = Author;
this.picture = Picture;
this.id = ID;
public static void main(String[] args) {
//test code here
public String getDescription(){
return this.description;
public String getTitle(){
return this.title;
public String getSubmitdate(){
return this.submitDate;
public String getEndDate(){
return this.endDate;
public String getAuthor(){
return this.author;
public String getPicture(){
return this.picture;
public String getNewsID(){
return this.id;

AIR DNS Caching

I recently read a question on StackOverflow which suggested that AIR may keep its own DNS cache separate from the OS it's running on (see: http://stackoverflow.com/questions/1251761/is-there-a-way-to-flush-the-dns-cache-or-force- a-host-name-to-re-resolve-in-adobe). I was wondering if anyone could confirm or deny that this is the case?
We noticed the issue because we were using some elastic IPs from Amazon and were contacted by someone who was assigned one of our recently freed IPs and suddenly had our AIR apps hitting their servers. I believe the issue only occurred for http requests (using URLRequest and URLLoader objects).
If it is the case that AIR is keeping its own DNS cache, is there a way to programmatically disable it or at least trigger it to refresh? (Looking for an answer from an Adobe Employee / AIR Dev, although feel free to chime in if you've noticed this too).
Thanks.

"dns listen" command has to be configured with the name and ip address of your dns server. You can use the "dns pin" command to do this.
http://www.cisco.com/univercd/cc/td/doc/product/webscale/uce/acns50/cref50/14623ref.htm#2408858
DNS-caching on the CE is not a "caching dns server". It is only for the CE to use itself - and not to point the PC's "dns server" at. DNS is only needed in Proxy mode.

DNS Cache location?

I'm just curious where OS X Server 10.6 stores its DNS cache or if there is a Terminal command I can use to display all of the caches from my network.
Thanks!

Check the system logs. See if there's an error on that end indicating any additional details of the problem. (The management port access is understandably restricted.)
This might require setting up /etc/rndc.conf by running rndc-confgen - have a look at the bind9 documentation and at the man pages for rndc and rndc.conf and rndc-confgen and Google around - and this will allow you to authenticate into the management port of the DNS server.
It's also rare that there's a need to flush the DNS caches.

DNS caching problem when configuring Windows clients for SCAN

I have a Windows 2008 R2 server running apps that connect to a RAC cluster database using the SCAN address. The SCAN address however always returns the same IP when you ping it from that server. If I flush the DNS cache I get a different address, but again the same one all the time. I believe this is caused by the fact that DNS caching is enabled on Windows by default. This has caused problems when one of the RAC nodes goes south and the cached SCAN IP is not responding. The applications lose their connections, try to reconnect, but can't because they keep using the same dead SCAN IP.
I suggested we disable the DNS Client service on those machines so that the SCAN name correctly cycles through the addresses but the Windows admin says not to do this. Is there a documented practice somewhere that this is OK to do for Windows RAC clients? Or is there a way to disable caching just on the SCAN name but leave it enabled from every other host name?
TIA

What happened was the SCAN VIP did not fail over. The node VIP did not fail over. The database instance was running but I could not connect to it even locally as sysdba. I got the message "protocol adapter error". This normally only occurs on Windows for local connections when either (a) the Oracle service is not running, or (b) you didn't set the ORACLE_SID variable correctly. Neither was true.
I tried "crsctl stop crs" but it could not stop the listeners.
I rebooted the server. During the reboot, neither the VIP no SCAN VIPs failed over. It's almost as if CRS either didnt recognize tat the other node had been shutdown, or it didn't care.
I have never seen this happen before.
For the record this is Oracle RAC 11.2.0.1.

Flush the DNS cache

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