I am having a problem with Java DB that I just don't know how to resolve. I am creating a DB and connecting to it using Java DB's native JDBC driver. If I relocate that database physically and try to connect to it using its new path, I consistently get XJ004 errors:
ERROR XJ004: Database 'blahblah' not found.
I am sure I am using the correct connection string. Is there any possibility the DB is somehow getting corrupted? Or is there some encoding of the DB path in the DB such that if you relocate a Java DB it gets confused?
I'm really at a loss here. :( Please help!
Jim
Have you verified that this error message isn't also used when there's no listener on the host machine ... and were you using JavaDB on your local machine before the relocation? Many database systems (and I'm not that familiar with JavaDB) ship set-up to only allow connections from localhost for security reasons. On PostgreSQL for instance, you have to allow TCP connections and bounce the daemon to obtain a remote connection.
Anyway ... since the problem started when you when remote, look for issues related to that first! (And if you can run your application on the remote machine, does that work?)
There must be a file named derby.log somewhere. Check the error there. If it is not detailed enough, try setting derby.stream.error.logSeverityLevel to a lower value. See the manual for more information.
Related
I have a remote Linux server and I want to connect to an Oracle database which is in another server, using ojdbc7 lib
When I try to connect directly to the database from my Windows PC, using the same client and ojdbc7 lib, I have reasonable connection time.
Now, when I want to connect through my linux server, I get extreme slowness, just in the connection time. . Once connected, the execution is OK.
I have read about adding -Djava.security.egd=file:/dev/urandom like in this post, but nothing happened.
What could I do to fix this delay in setting up a connection from linux?
Close, but no cigar: it's "file:///dev/urandom", or one of the variations, see eg. https://anirban-m.blogspot.com/2014/03/jdbc-connection-reset-error-java.html
I noticed you are using version 12.1.0.1.
There was an Oracle bug where JDBC connections could take excessive times because the data being sent required the listener to perform a DNS lookup for each connection and that could apparently be very slow for some reason.
The bug was fixed in 12.2 and there is a back-ported fix (patch) for 12.1.0.2.
In the meantime, try getting your Linux admin to go through the process of tuning DNS lookups on that server. E.g., tune /etc/resolv.conf or enable the name service cache daemon. I'm not really expert in Linux administration so I can't help you. But based on the problem and the version you are using, that's where I'd look.
Sorry Maybe this is the second time I am Asking this question because of not getting any answers .
this is my Code
try{
File f = new File("Database.sql");
if(f.exists()){
Class.forName("com.mysql.jdbc.Driver").newInstance();
Connection con = DriverManager.getConnection("jdbc:mysql://localhost/"+f.getName(),"","");
}else{
f.createNewFile();
System.out.println("file created");
//also do the connection
}
}catch(Exception ex){
System.out.println(ex.getMessage());
}
and Here is the error :
Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
The purpose of this question is:
I am creating an Application that is for many users, the problem is they don't know anything about computer and I must make it as simple as possible.
So is there any way to connect with MYSQL like MS ACCESS via Directory Path ?
OR is there any other suggestion instead ?
Thanks .
AFAIK, you can't plug in a file name in the JDBC url for MySQL. MySQL needs to be running, and you need to connect to it via its TCP port. Something like:
jdbc:mysql://localhost:3306/yourDatabaseName
See http://dev.mysql.com/doc/refman/5.6/en/connector-j-reference-configuration-properties.html
Preliminary definitions
"Connect to a MySQL database file" is improper phrasing.
One actually connects to a MySQL database server, which allows access to a database. And so there must be a MySQL server to connect to, more about that below.
Your Database.sql file is a database dump file, that is to say, a dumb (plain text) file. You need a specialized process to extract data from it, after interpreting your SQL queries: a database server.
You might be assuming that one can connect to a file because you are used to working with MS Access files. I am not an expert neither in Java nor in MS Access, but it is my undestanding that accessing a MS Access "database" file from Java actually means connecting to some middleware server, such as this ODBC thingy from Microsoft.
The answer
There is no way to connect to a MySQL database server via a directory path. The only native ways are:
TCP
Local socket (Unix servers only)
Named pipes (Windows servers only)
Shared memory (Windows servers only)
There could be some third-party pieces of software around that provide other protocols, which I am not aware of, but they all reduce to the same problem: there must be a MySQL sever running somewhere.
On second thought there is actually one way to access MySQL data without an external MySQL server running: the embedded MySQL server C library. I never tried it myself, but it looks like a viable option for stand-alone applications. I do not believe, however, that it is a desirable solution if you plan to share the same MySQL data across several processes or computers.
The workarounds
Now I understand you are building a Java desktop application based on data that you have in the form of a SQL dump file, probably dumped from a MySQL server. If you want your users to be able to access this data from this Java application, I can see a few options:
Install a MySQL server on their computers and load this dump into it. Obvious as hell, but impractical, if I hear you well. Although I guess this installation could certainly be performed automatically by your Java application.
Install a MySQL server on a machine of your own, and make it accessible from your users' computers. Major drawback: it requires your users to be connected. You would also probably want to create a distinct database for each user.
Use an actually serverless database engine such as SQLite. This seems to be the best option for you. Its SQL syntax is virtually identical to MySQL for usual operations. There must be plenty of JDBC drivers for it. Again, I am not the best advisor in Java, but this one seems to be a serious candidate.
I am new to Oracle, and am trying to run a simple example code with Java, but am getting this error when executing the code.. I am able to start up the listener via CMD and am also able to run SQL Plus. Can anyone give me a hand and tell me what I might be doing wrong?
Update:
I am using JDBC.
Database is local, and I actually had it working but it stopped working just today. I'm not really sure why though. Would you mind giving me some procedures to follow by since I don't know much.
Either:
The database isn't running
You got the URL wrong
There is a firewall in the way.
(This strange error message is produced by Oracle's JDBC driver when it can't connect to the database server. 'Network adapter' appears to refer to some component of their code, which isn't very useful. Real network adapters (NICs) don't establish connections at all: TCP protocol stacks do that. It would have been a lot more useful if they had just let the original ConnectException be thrown, or at least used its error message and let it appear in the stack trace.)
I had the same problem, and this is how I fixed it.
I was using the wrong port for my connection.
private final String DB_URL = "jdbc:oracle:thin:#localhost:1521:orcll"; // 1521 my wrong port
go to your localhost
(my localhost address) : https://localhost:1158/em
login
user name
password
connect as --> normal
Below 'General' click on LISTENER_localhost
look at you port number
Net Address (ADDRESS=(PROTOCOL=TCP)(HOST=localhost)(PORT=1522))
Connect to port 1522
Edit you connection
change port 1521 to 1522.
done
Another thing you might want to check that the listener.ora file matches the way you are trying to connect to the DB. If you were connecting via a localhost reference and your listener.ora file got changed from:
HOST = localhost
to
HOST = 192.168.XX.XX
then this can cause the error that you had unless you update your hosts file to accommodate for this. Someone might have made this change to allow for remote connections to the DB from other machines.
I figured out that in my case, my database was in different subnet than the subnet from where i was trying to access the db.
I had this error when i renamed the pc in the windows-properties. The pc-name must be updated in the listener.ora-file
Most probably you have listener configured wrongly, the hostname you specify in connection string must be the same as in the listener.
First check the Firewall and network related issues.
Check if Oracle Listener service is available and running. If not you may use Oracle Net Configuration Assistant tool to add and register new listener.
If the above steps are ok then you need to configure Oracle Listener appropriately. You may use Oracle Net Manager tool or edit “%ORACLE_HOME%\network\admin\listener.ora” file manually.
There are 2 options that need to be considered carefully:
Listening Locations associated with the Listener – Hostname(IP) and Port in Listening Location must exactly match the ones used in the connection string.
For example, if you use 192.168.74.139 as target hostname, then there must be Listening Location registered with the same IP address.
Also make sure the you use the same SID as indicated in Database Service associated with the Listener.
https://adhoctuts.com/fix-oracle-io-error-the-network-adapter-could-not-establish-the-connection-error/
IO Error: The Network Adapter could not establish the connection (CONNECTION_ID=iKQM6lBbSLiArrYuDqud8A==)
if you are facing this issue
1- make sure you have downloaded oracle databases like oracle 11g,19c, 21c, or any latest databases.
2- search for services in your computer or type win+r then services.mis then search for oracleservice you will find orcl or xe or any other sid like oracleserviceorcl;
after that you can test your connection using sql developer, sql plus or cmd
To resolve the Network Adapter Error I had to remove the - in the name of the computer name.
In my case, I needed to specify a viahost and viauser. Worth trying if you're in a complex system. :)
For me the basic oracle only was not installed. Please ensure you have oracle installed and then try checking host and port.
I was having issues with this as well. I was using the jdbc connection string to connect to the database. The hostname was incorrectly configured in the string. I am using Mac, and the same string was being used on Windows machines without an issue. On my connection string, I had to make sure that I had the full url with the appending "organizationname.com" to the end of the hostname.
Hope this helps.
Just try to re-create connection. In my situation one of jdbc connection stopped working for no reason. From console sqlplus was working ok.
It took me 2 hours to realize that If i create the same connection - it works.
I've got a database that is mirrored using SQL 2008 Mirroring.
I have a java application, running on Linux, using the Microsoft SQL
type 4 JDBC drivers.
I have this setup duplicated as a QA environment.
On my QA environment, when I manually fail over the database,
providing a successful connection had already been made, the failover
was completely transparent. I did not have to implement anything in
order to get the application to talk to the new Principle (Old
mirror).
In the live environment however, the connections stop working once I
have manually failed over.
There are quite a few things different between the live and QA environments, but not anything I'd consider fundamental to this process, communication between databases is all very localised in both situations and there are no firewalls (Except the ones built into Windows Server 2008) between my java app and the Windows boxes running SQL 2008.
Does anyone have any ideas about how I can go about diagnosing this issue? Or can anyone tell me how this failover transparency occurs so I can work out how to diagnose this myself?
This behaviour is handled by the SQL Server provider as part of the Client Redirect behaviour. This was part of the SQL Server 2005 JDBC (Java Database Connectivity) 1.1 Driver, I'm unsure if that provider was directly used for the new type 4 drivers though?
In your live environment, is your application successfully connecting to the primary server before it fails over, so it is able to cache the failover partner and make use of that when the failover occurs?
To be sure, you can explicitly state the failover partner in the connection string, which is the recommended practice:
jdbc:sqlserver://serverA:1433; databaseName=AdventureWorks; integratedSecurity=true; failoverPartner=serverB
The full documentation of the redirect behaviour can be found here.
The addition of the failover documentation here suggests that it could be a manual consideration.
I am getting the error: "The Network Adapter could not establish the connection" from a web application deployed in Oracle Application Server 10g. The database is local, so there shouldn't be any connection issues.
First test: I can connect to the DB no problem from SQL plus, run queries, etc.
Second test: I can connect to the database no problem from a locally installed JDeveloper on the server, and run queries, etc. no problem. This works with the short JDBC scring, and the long one (shown below).
jdbc:oracle:thin:#(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=localhost)(PORT=1521)))(CONNECT_DATA=(SERVICE_NAME=abcd)(SERVER=DEDICATED)))
Yet when I run the web app, it gives the above error. It seems too generic for me to do anything about.
Any suggestions on how to solve this? I assume that Oracle logs failed connection attempts somewhere, but I couldn't find anything relevant in the databases alert.log file.
It is possible that the problem is that the application is using an old jsdk, but I would assume that then some version mismatch error would be given instead of a "network connection" message.
Edit: I don't know whether this is an OAS problem or a problem with the specific Web Application, I would like to figure this out first, as it seems it should be easy. In WebSphere, there is a "test connection" button to dest data-sources you have added, but it seems there is no such functionality in OAS10? Somehow I think there must be, and I am just missing it because I am not an OAS expert.
Edit 2: I installed JDevelop on a remote machine and connected to the database with no problems, so I know for sure it isn't an issue with the database connectivity itself - it seems like it must be a problem within OAS?
I faced similar problem(able to connect through client but not web application) with Oracle XE when running with default configuration. Increasing number of sessions and processes solved my problem. Check this http://www.markcallen.com/oracle/oracle-xe-tuning.
I assume that Oracle logs failed connection attempts somewhere
It would show up in listener.log, but with the error you get, it seems doubtful that JDBC could even contact the listener.
jdbc:oracle:thin:#(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=localhost)(PORT=1521)))(CONNECT_DATA=(SERVICE_NAME=abcd)(SERVER=DEDICATED)))
Is that the same string you use for the web app?
I've had issues with localhost and 127.0.0.1 which go away when using a more definitive host name or address [IE a name that other machines would know the host as.]. I think it was to do with how the name was resolved (eg locally or off to a name server or similar).
Not a java person, but is there any way to simply ping localhost/127.0.0.1 from the java and see whether there's a response.
One of the ways to fix the issueis to update Hosts file at WAS Server with entries for DB servers as shown below:
111.222.333.444 serverab.abc.com serverab