MS ACCESS dirty reads

I have a JSP page that adds (or updates) a record to an MS ACCESS table and then forwards control to a second JSP page that queries the table. The problem is that second page does not find the new record (except occassionally). If the page is refreshed the record appears. Autocommit is set to true.
Other than delaying the JSP, so ACCESS has more time to make the update, does anybody have any suggestions how this can be solved.
Thanks
Richard

I don't know if it's the same, if you use JSP.
But in use from usual applications Access seems to have this bug, that always the last inserted or updated row doesn't show its change unless
1) the connection is closed or
2) the next select is done on this table.
2) seems to be the best workaround: simply do a dummy select each time after finishing the changes.

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Able to make dirty read using Oracle 9i and JDBC thin driver v 9.2.0

I've searched this forum and did not see anything to directly answer my question.
I checked the Oracle JDBC Frequently Asked Questions...
ditto (perhaps due to the fact that it was last updated: 22 June 2001).
So here is my question, and thank you in advance for any insight (apologies if I have missed finding an already answered question):
Section 19-15 of:
"JDBC Developerâs Guide and Reference"
(which is for Oracle 9i database)
downloadable from:
http://download-east.oracle.com/docs/cd/B10501_01/java.920/a96654.pdf
is entitled:
"Transaction Isolation Levels and Access Modes"
The section seems to indicate that
if JDBC connection A is setup with:
setAutoCommit(false)
setTransactionIsolation(Connection.TRANSACTION_READ_COMMITTED)
and then used to perform an update on a row (no commit(), rollback(), or close() yet) ...
then JDBC connection B (setup in the same way) will be prevented from
making a dirty read of that same row.
While this behavior (row-level locking) occurs correctly when using MS SQL Server 2000,
it is not occuring correctly with Oracle 9i and the Oracle Thin JDBC driver version 9.2.0.
The test case I have shows that with Oracle, connection B is able to make a dirty read
successfully in this case.
Am I doing something wrong here ?
Again, MS SQL Server correctly blocks connection B from making the Read until Connection A
has been either committed, rolled back, or closed, at which time connection B is able to
complete the read because the row is now unlocked.
Is there a switch I must throw here ?
Again, any help is greatly appreciated.

Thanks for the response.
I understand what you are saying...
that readers don't block writers in Oracle (the same is true in SQL Server 2000).
However, I don't see how my test case is working correctly with Oracle (the exact same code acting as I'm thinking it should with SQL Server, but I still think it is acting incorrectly with Oracle).
I have transaction A do this:
update <table> set <column2>=<value> where <column1>='1'
then I use Thread.sleep() to make that program hang around for a few minutes.
Meanwhile I sneak off and start another program which begins transaction B. I have transaction B do this:
select * from <table> where <column1>='1'
and the read works immediately (no blocking... just as you have said) however, transaction A is still sleeping, it has not called commit() or rollback() yet.
So what if transaction A were to call rollback(), the value read by transaction B would be incorrect wouldn't it ?
Both A and B use setAutoCommit(false) to start their transactions, and then call setTransactionIsolation(Connection.TRANSACTION_READ_COMMITTED).
Isn't that supposed to guarantee that a reader can only read what is committed ?
And if a row is in "flux"... in the process of having one or more values changed, then the database cannot say what the value will be ?
I can almost see what you are saying.
In letting the reader have what it wants without making it wait, I suppose it could be said that Oracle is holding true to the "only let committed data be read"
So if that's it, then what if I want the blocking ?
I want an entire row to be locked until whoever it in the middle of updating, adding, or removing it has finished.
Do you know if that can be done with Oracle ? And how ?
Thanks again for helping me.

Unable to access adobe reader on macbook pro 10.7.5

please provide assistance with accessing adobe reader I have updated the iOS software and unable to complete an adobe update, will not allow me to complete step 3. thank you Tracey

[moved to the Adobe Reader (desktop) forum]
If you have Adobe Reader on a MacBook Pro (laptop computer), the operating system is Mac OS X (not iOS).

How do I access adobe reader since I did a trial of acrobat pro?

Since I did a trial of acrobat pro and declined to buy at the moment, the system is not letting me access adobe reader. How can I rectify this without buying a version of acrobat? many thanks,

Hi Test Screen Name, that seems to have worked. Many thanks!
Trainer Walt
Re: How do I access adobe reader since I did a trial of acrobat pro?
created by Test Screen Name <http://forums.adobe.com/people/TestScreenName> in Adobe Reader - View the full discussion <http://forums.adobe.com/message/5906147#5906147

Access my Reading List from PC?

Is there are way to access my Reading List that created on iPhone/iPad, on my PC through iCloud? I don't use Safari.
Or alternatively it would be nice to be able to email the Reading List...

Hello modance
Check out the article below for troubleshooting bookmarks and access to your reading list.
iCloud: Troubleshooting iCloud Bookmarks and Reading List
http://support.apple.com/kb/TS4001
Thanks for using Apple Support Communities.
Regards,
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Does apple make a common access card reader?

Does MAC make a common access card reader?

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Unable to access only Read Write addresses of AB Micrologix 1400 PLC using NI DSC and NI OPC server

Hi,
I have been using NI DSC and OPC servers (NI and Kepware) to communicate with Allen Bradley Micrologix 1400 PLC (1766-L32BXB). Recently at one site I found that I could access Process values from the PLC correctly (Read Only tags) but could not access the Read Write Tags at all. The latter are addresses to which it should be possible to write Set (i.e., references) values from MMI or PC software. I am able to do so from the MMI not from the PC software. I get communication error message on the MMI and PC, mentioning the PLC address being accessed (e.g. N7:0).
Support from the supplier is not available. Hence can anyone let me know if ladder logic could have been written to prevent PC software based access of Read/write addresses (N7:0 to 9 in this case), while permitting access to Read only addresses? Is the problem at the PLC end or OPC server end? Is there a way to get around this?
Thanks in advance.

The OPC Server cannot force Outputs so if th registers in question are the outputs of ladder rungs you cannot write to them via the server. The controller will accept the write from the server but will not execute the write. In some cases the server event log will post an error if it is the PLC. Do you get errors when you try to write and if so what are the posted error messages.
Fred Loveless
Kepware Technologies
http://www.kepware.com

InitCVIRTE generates error message "Unhandled exception in "MyApp.exe": 0xC0000005: Access violation reading location 0x00000000."

Hi,
I have converted a LabWindows CVI project to Visual Studio 2005. When I start the application i debug mode I get the message "Unhandled exception at 0x685662ba in EE352-500V.exe: 0xC0000005: Access violation reading location 0x00000000."
It comes when the application calls: InitCVIRTE in this context:
int __stdcall WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpszCmdLine, int nCmdShow)
// Initialize LabWindows/CVI run-time library
if (InitCVIRTE (hInstance, 0, 0) == 0)
return -1; /* out of memory */
The debugger indicates that value of hInstance is 0x00400000 {unused=9460301}
Can someone give me a solution to this problem. I have done some search on the Web without success.
Thanks!

I think that exception might be coming from the data execution prevention service that is part of Win XP SP2. The OS thinks that you're somehow trying to execute in the data segment and kills the process. It's intended to catch worms and viruses.
You can turn this service off for non-Microsoft programs using the control panel.
Many pointer handling errors now report as this exception instead of as a memory violation exception. That looks like a null pointer derefence to me.
Menchar
Message Edited by menchar on 11-09-2007 07:12 PM

Dirty reads vs phantom reads

Hi,
What is the difference between a "Dirty Read" and "Phantom Reads". Can anyone explain in brief or give an example?
Thanks in advance.

A dirty read is an uncommitted read, which may or may not be exist in the table. A phantom is a ghost record that doesn't appear in a transaction initially but appears if it is read again because some other transaction has inserted rows matching the criteria.
Here are examples of both:
--Dirty read example
create table t1 (c1 int null, c2 varchar(50) null)
go
insert t1(c1, c2) values (1, 'one')
insert t1(c1, c2) values (2, 'two')
insert t1(c1, c2) values (3, 'three')
insert t1(c1, c2) values (4, 'four')
begin tran
update t1 set c2 = 'zero'
-- let this run in the current query window and open a new query window to run the below statement
--and you will see all 4 rows having a value of 0 in column c2, which is uncommitted data
select * from t1 with (nolock)
--uncomment this and run the below statement and rerun the above statement
--and you will see the previous values of one, two, three and four
--rollback tran
Here's an example of a phantom reads:
--Phantom example
create table t1 (c1 int null, c2 varchar(50) null)
go
insert t1(c1, c2) values (1, 'one')
insert t1(c1, c2) values (2, 'two')
insert t1(c1, c2) values (3, 'three')
insert t1(c1, c2) values (4, 'four')
-- let this run in the current first query window and open a second query window to run the below statement
--and you will see all 2 rows having a value in column c2 starting with character t
begin tran
select * from t1
where c2 like 't%'
--now insert the new value of ten (matching the query criteria - starts with t) from the first query window
insert t1(c1, c2) values (10, 'ten')
--Run the below statement again from the second query window that is open and you will see the new row
--that got inserted - so 3 rows are seen including the newly inserted ten
--this new row is a phantom read
select * from t1
where c2 like 't%'
--uncomment this and run the below statement in the second query window
--rollback tran
Satish Kartan www.sqlfood.com

Dirty read on informix XA datasource

Hi,
I'm not able to set the transaction isolation level to dirty read with informix XA driver. I tried the following options.
1. Setting the initSQL - I set the initSQL property to SQL SET ISOLATION TO DIRTY READ
2. Setting the IFX_ISOLATION_LEVEL - I tried adding the property IFX_ISOLATION_LEVEL=1
Note: I have used informix driver com.informix.jdbcx.IfxXADataSource
Setting the IFX_ISOLATION_LEVEL property on non XA data source (driver-com.informix.jdbc.IfxDriver) works fine, but the same configuration does not work on XA resource.
Also the link http://download.oracle.com/docs/cd/E13222_01/wls/docs90/jdbc_drivers/informix.html#1065880 mentions about setting the data source with weblogic driver, but it does not mention about the property need to be set for isolation level.
Can you please help.
I'm using weblogic 10.0 server.

I want to read uncommitted data from data base. I created two data source one XA and other Non XA, and I wrote a small application to lookup the data source and to print the isolation level of the connection. The Non XA connection is printing isolation level 1 which is what I wanted, but for XA connection the isolation level is printed as 2 which is the default isolation level READ COMMITTED. Also I inserted a record in some transaction and tried to read using the looked up data source, with Non XA connection I'm able to read the data but with XA connection I'm not able to read the data, instead i'm getting 'java.sql.SQLException: Could not position within a file via an index'.

Dirty read with READ COMMITTED and sql count.

Hi,
Under read committed isolation level a select count(*) ... return 1, in fact the select sees insert during other current transaction, it is typically a dirty read. But a select without count function return 0. Can someone explain me why I have this behaviour ?
the transaction which is making the select count(*)...has read committed isolation level
the transaction which has inserted the new item has read uncommitted isolation level
Please tell me if I am missing something.
I am using Maxdb 7.6.
Thx

Hi there,
ok, I tried again an was actually able to reproduce the behavior
The problem here is the special implementation of the count (*) function.
To get correct results (isolation level wise), you may use count(<primary key>) instead.
So for your example
select count (IDDI) from NONO.APPA
should always deliver the correct result.
The same is true for the other aggreation functions (min/max/avg...) - it's just about the very special count(*) handling here.
I informed our development about this.
thanks for pointing out!
Lars

Access violation reading location 0x00000661.

Hi, I have this following code here:
int *Fibonacci = new int[];
Fibonacci[0] = 1;
Fibonacci[1] = 1;
Fibonacci[2] = 2;
int FinalVal = 0;
int Iter = 3;
while (FinalVal<10^9)
Fibonacci[Iter] = Fibonacci[Iter - 2] + Fibonacci[Iter - 1];
cout << Fibonacci[Iter] << endl;
FinalVal = Fibonacci[Iter];
Iter = Iter + 1;
delete [] Fibonacci;
and the application keeps screaming about Access violation reading location 0x00000661. I've already tried using Call Stack and all I can know that it's crashing down at Index 16 (1597 number of fibonacci). I've no idea why it stops in this particulary
moment, any suggestions?

On 2/9/2015 5:28 PM, Alieniasty wrote:
[code]
int *Fibonacci = new int[];
This allocates just one byte (I'm surprised it even compiles; I'm pretty sure it shouldn't). You must specify the size for the array you want to allocate.
while (FinalVal<10^9)
10 ^ 9 doesn't do what you think it does. ^ is a binary-XOR operator. It so happens that 10 ^ 9 == 3
Igor Tandetnik

Dirty reads

hi ,
What are dirty reads ?
Can someone point me to a good document for understanding dirty reads ?
Rgds
S

WIP wrote:
What are dirty reads ?In simple terms using a basic example:
sessionA locks a row for an update. It makes changes to the row. sessionB wants to read the same row - but cannot as due to the way that database is designed. That row is locked. So sessionB tells the database it wants a dirty read instead - that it does not care whether some rows are locked or not. This means that now sessionB reads rows via a cursor, and some of these could be locked rows and the data of these rows can be dirty - dirty meaning that the data is not committed data and can be rolled back. The dirty read therefore does not return a consistent set of row data.
Can someone point me to a good document for understanding dirty reads ?Not applicable to Oracle as there is no such concept as dirty reads in Oracle. All reads in Oracle is consistent - in basic terms, you only read committed data (unless you read your own uncommitted changes). And writers (processes locking and changing rows) never block readers.

How do you implement 'Dirty Read/ Write' concept?

Hi,
I need to implement dirty read/ write concept into my procedure. I wanted to know how to go about it. Does Oracle have provide a way to do this or is this something to be worked out with some logic manually?
Can someone suggest the exact logic I should follow or chalk out a simple algorithm.
Any kind of information on this would be much appreciated.
Thanks,
Amrita.

Sorry for this late reply.<br>
My first reply should have contained an example on how to implement it for the kicks. Don't use this code for anything else but a test. It's absolutely worthless application-wise. But it proves that some dirty read/write functionality can be obtained if one twists everything that is good. Here goes. First I create two java classes and two PL/SQL "wrappers". Then - simply connect with session 1 and invoke exec dirty_write<br>
make no commit ... and let session 2 select dirty_read from dual. You'll notice that the data written by session 1 is read by session 2.<br>
create or replace and compile
java source named "FileAppendTest"
as
import java.io.File;
import java.io.FileOutputStream;
public class FileAppendTest {
static public void append() {
try {
    int vSomethingToWrite = 9;
   File vFile = new File("c:\\db_out.txt");
   FileOutputStream vAppendFile = new FileOutputStream(vFile, true);
   vAppendFile.write ( vSomethingToWrite );
vAppendFile.close();
} catch (Exception e) {
   // let this test hide all errors
create or replace and compile
java source named "DirtyReadTest"
as
import java.io.File;
import java.io.FileInputStream;
import java.io.File;
import java.io.FileInputStream;
public class DirtyReadTest {
static public int read() {
int vError = 0;
try {
   File vFile = new File("c:\\db_out.txt");
   FileInputStream vReadFile = new FileInputStream(vFile);
   return vReadFile.read();
} catch (Exception e) {
   return vError;
create or replace procedure dirty_write as
language java
name 'FileAppendTest.append()';
create or replace function dirty_read return number as
language java
name 'DirtyReadTest.read() return integer';
-- as I mentioned earlier. Only try this code for the fun of it. Don't consider it for anything remotely usable in an application.

Error: Accessing the Reader Extensions Server web application for the first time

Hi,
I've followed the the installation guide line by line. Everything OK.
But when i access the Reader Extensions Server web application i see the following error:
An error has occured
Error 473: The credential permission settings could not be determined: 'com.adobe.document.pdf.CredentialLoginFailure: IDL:com/adobe/document/pdf/CredentialLoginFailure:1.0'.
Have you ever faced this kind of message before?
To tell you the truth i'm not very sure if my Rights Credential file is valid. But is this the cause of this message?
I use Form Server 6 and Reader Extensions 6 with a Websphere Application Server 6.0
Thanks in advance

Hi Stelios,
Yes, it seems to me also, as a bad certificate issue.
If memory serves, I run into this message once, where the certificate was valid. Anyway, Websphere v6 is not a supported app server. Have you tried installing on v5.1?
You might want to read this post, too:
matt cockburn, "Fix for LiveCycle Reader Extensions 7.0 install error" #, 6 May 2005 8:22 am
If you are located in Greece, we may be able to help you. You may contact me "ekokkoris at anodos.gr", should you wish.
Regards,
Evangelos

MS ACCESS dirty reads

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