let me try to explain the problem in general parlance.
We are using SQLite 3.7.11 by System.Data.SQLite Wrapper for .NetCF in Version 1.0.80.
We have two database files:
master_data.db
inventory.db
We establish a read-only connection to master_data.db to display some information to the user.
Data Source=master_data.db;Version=3;Read Only=true;Journal Mode=OFF;Synchronous=OFF;
We establish a writable connection to inventory.db to update/insert inventory information depending on some information from master_data.db
Data Source=inventory.db;Version=3;Journal Mode=DELETE;Synchronous=OFF;
To allow consistency checks in update/insert statements, we attach the master_data.db to this connection.
ATTACH 'master_data.db' AS md_db
We start a transaction at inventory.db
SQLiteTransaction tx = connection.BeginTransaction();
We update a simple table in inventory.db without interaction of master_data.db.
using (IDbCommand cmd = connection.CreateCommand())
{
cmd.CommandText = #"UPDATE header_info SET count_time = #countTime";
SQLiteParameterparam = new SQLiteParameter("#countTime",
DateTime.Now.ToUniversalTime())
cmd.Parameters.Add(param)
return cmd.ExecuteNonQuery();
}
We commit the changes and it will hang until timeout occurs and SQLITE_BUSY is raised.
tx.Commit();// BAAM! due to SQLITE_BUSY
We do not understand what's wrong here. The established read-only connection to master_data.db cannot lock the whole database. Even if there is a second and writable (the only one) connection due to the ATTACH command - which was executed by the one and only writable inventory.db connection. We are sure ther is no second connection to inventory.db.
[EDIT]
In the case of error no other transaction to master_data.db is open. Even the connection is not in use but open.
[/EDIT]
May this issue, we are also facing, be part of the problem? SQLite: Multiple Connections to one file - the one and only writable is not persisted
Thanks for your help.
Regards,
Schibbl
When you have attached databases, a transaction always covers all those databases.
So when you want to write to a database, you have to ensure that no other connection has any open transaction on the main database or on any of the attached databases.
Related
I am working on a migration project where we are migrating one application from Weblogic to Websphere 8.5 server.
In Weblogic server, we can specify default schema while creating datasource but I don't see same option in WebSpehere 8.5 server.
Is there any custom property through which we can set it , I tried currentSchema=MySchema but it did not work.
This answer requires significantly more work, but I'm including it because it's the designed solution to customize pretty much anything about a connection, including the schema. WebSphere Application Sever allows you to provide/extend a DataStoreHelper.
Knowledge Center document on providing a custom DataStoreHelper
In this case, you can extend com.ibm.websphere.rsadapter.Oracle11gDataStoreHelper.
JavaDoc for Oracle11gDataStoreHelper
The following methods will be of interest:
doConnectionSetup, which performs one-time initialization on a connection when it is first created
doConnectionCleanup, which resets connection state before returning it to the connection pool.
When you override doConnectionSetup, you are supplied with the newly created connection, upon which you can do,
super.doConnectionSetup(connection);
Statement stmt = connection.createStatement();
try {
stmt.execute(sqlToUpdateSchema);
} finally {
stmt.close();
}
doConnectionCleanup lets you account for the possibility that application code that is using the connection might switch the schema to something else. doConnectionCleanup gives you the opportunity to reset it. Again, you are supplied with a connection, upon which you can do,
super.doConnectionCleanup(connection);
Statement stmt = connection.createStatement();
try {
stmt.execute(sqlToUpdateSchema);
} finally {
stmt.close();
}
Note that in both cases, invoking the corresponding super class method is important to ensure you don't wipe out the database-specific initialization/cleanup code that WebSphere Application Server has built in based on the database.
As far as I know Weblogic only allows setting a default schema by setting the 'Init SQLto a SQL string which sets the current schema in the database, such asSQL ALTER SESSION SET CURRENT_SCHEMA=MySchema`. So, this answer is assuming the only way to set the current schema of a data source is via SQL.
In WebSphere, the closest thing to WebLogic's Init SQL is the preTestSQLString property on WebSphere.
The idea of the preTestSQLString property is that WebSphere will execute a very simple SQL statement to verify that you can connect to your database properly when the server is starting. Typically values for this property are really basic things like select 1 from dual', but since you can put in whatever SQL you want, you could setpreTestSQLStringtoSQL ALTER SESSION SET CURRENT_SCHEMA=MySchema`.
Steps from the WebSphere documentation (link):
In the administrative console, click Resources > JDBC providers.
Select a provider and click Data Sources under Additional properties.
Select a data source and click WebSphere Application Server data source properties under Additional properties.
Select the PreTest Connections check box.
Type a value for the PreTest Connection Retry Interval, which is measured in seconds. This property determines the frequency with which a new connection request is made after a pretest operation fails.
Type a valid SQL statement for the PreTest SQL String. Use a reliable SQL command, with minimal performance impact; this statement is processed each time a connection is obtained from the free pool.
For example, "select 1 from dual" in oracle or "SQL select 1" in SQL Server.
Universal Connection Pool (UCP) is a Java connection pool and the whitepaper "UCP with Webshere" shows how to set up UCP as a datasource.
for JDBC datasource, the steps are similar but, you can choose the default JDBC driver option.
Check out the paper for reference.
I got an asp.net gridview connected to my sql database. When Inserting a new record or updating a record im doing some serverside checks and then either update/insert a record or do nothing. right now i got 2 methods CheckArtistExists and CheckSongExists which are both using a SqlConnection Object e.g.
public bool CheckSongExists(string _title, int _artistId)
{
int cnt = -1;
using (SqlConnection con = new SqlConnection(CS))
{
//check if song already is exists in DB
SqlCommand cmd = new SqlCommand("Select Count(ID) from tblSong WHERE Title = #newTitle AND ArtistId = #newArtistId;", con);
cmd.Parameters.AddWithValue(#"newTitle", _title);
cmd.Parameters.AddWithValue(#"newArtistId", _artistId);
con.Open();
cnt = (int)cmd.ExecuteScalar();
// if cnt ==1 song exists in DB, of cnt == 0 song doesnt exist
if(cnt == 1)
{ return true; }
else
{ return false; }
}
}
So for the Update function in the gridview i need to establish 3 SqlConnections (at max) one to check for the artist(if artist doesnt exist i have to insert a record to tblArtist first)
then a check if the song exists(only if artist exists) and finally if song doesnt exist I have to insert a new record.
I know database connections are valuable resources thats why i put them in a using block. So im not quite sure if its good style to use 3 SqlConnection objects to update/insert. Can you please tell me if my code is ok or if i should rather use another approach for this problem.
thank you
ADO.NET internally manages the underlying Connections to the DBMS in the ADO-NET Connection-Pool:
In practice, most applications use only one or a few different
configurations for connections. This means that during application
execution, many identical connections will be repeatedly opened and
closed. To minimize the cost of opening connections, ADO.NET uses an
optimization technique called connection pooling.
Connection pooling reduces the number of times that new connections
must be opened. The pooler maintains ownership of the physical
connection. It manages connections by keeping alive a set of active
connections for each given connection configuration. Whenever a user
calls Open on a connection, the pooler looks for an available
connection in the pool. If a pooled connection is available, it
returns it to the caller instead of opening a new connection. When the
application calls Close on the connection, the pooler returns it to
the pooled set of active connections instead of closing it. Once the
connection is returned to the pool, it is ready to be reused on the
next Open call.
So obviously there's no reason to avoid creating,opening or closing connections since actually they aren't created, opened and closed at all. This is "only" a flag for the connection pool to know when a connection can be reused or not. But it's a very important flag, because if a connection is "in use"(the connection pool assumes), a new physical connection must be openend to the DBMS what is very expensive.
So you're gaining no performance improvement if you "reuse" connections but the opposite.
Create, open(in case of Connections), use, close and dispose them where you need them(f.e. in a method)
use the using-statement to dispose and close(in case of Connections) implicitely
So yes, it's absolutely fine to use one connection per method since you are not using a physical connection at all if connection-pooling is enabled (default).
Another question is if you could improve your approach. You could create a stored-procedure which checks existence and updates or inserts accordingly.
Solutions for INSERT OR UPDATE on SQL Server
Suddenly INSERT, UPDATE and DELETE fails for a certain file (a table in a remote system which I believe is an AS/400).
The linked server that we make use of is set up in SQL Server, and it's using an ODBC data source (DSN). The Data source is an "ODBC-data source for iSeries Access for Windows".
Only one single table has this problem. We can make inserts and updates in other tables using the same linked server, without any errors, and SELECTs still work for the problematic table.
We get these messages for INSERT and UPDATE statements (server and DB names replaced in the code below):
Msg 7399, Level 16, State 1, Line 1
The OLE DB provider "MSDASQL" for linked server "MYSERVER" reported an error.
The provider did not give any information about the error.
Msg 7343, Level 16, State 2, Line 1
The OLE DB provider "MSDASQL" for linked server "MYSERVER" could not INSERT INTO
table "[MYSERVER].[MYDB].[DMPCOM].[DMPXIF]". Unknown provider error.
And DELETE gives this message:
The OLE DB provider "MSDASQL" for linked server "MYSERVER" could not delete from
table ""MYDB"."DMPCOM"."DMPXIF"". There was a recoverable, provider-specific
error, such as an RPC failure.
If you have any clues to this, please don't hesitate to answer this question.
Thanks,
Andreas
The reason to the error was that journalling had been turned off on the AS400 file, that we connect to from SQL Server using linked server and an ODBC iSeries datasource. This had also turned commitment control off.
Setting commit to "Commit immediate (*NONE)" on the ODBC iSeries datasource did however not help. (Perhaps there is more to it than changing that setting.)
The database administrator of the AS/400 system recreated the table with its default settings, including journaling and commitment control, and then it was all back to normal, and insert, update and delete worked, from the linked server connection.
I'm using SQL Server and ASP.NET. I have the following function:
Using js = daoFactory.CreateJoinScope()
Using tran = New Transactions.TransactionScope()
'...
tran.Complete()
End Using
End Using
However, the following exception is thrown:
The transaction manager has disabled its support for remote/network transactions.
Description of JoinScope:
Public Class JoinScope
Implements IJoinScope
Implements IDisposable
'...
End Class
I have worked this way in another application with the same environment without a problem, but here I have this problem. What could I do to fix the issue?
Make sure that the "Distributed Transaction Coordinator" Service is
running on both database and client.
Also make sure you check "Network DTC Access", "Allow Remote Client",
"Allow Inbound/Outbound" and "Enable TIP".
To enable Network DTC Access for MS DTC transactions
Open the Component Services snap-in.
To open Component Services, click Start. In the search box, type dcomcnfg, and then press ENTER.
Expand the console tree to locate the DTC (for example, Local DTC) for which you want to enable Network MS DTC Access.
On the Action menu, click Properties.
Click the Security tab and make the following changes:
In Security Settings, select the Network DTC Access check box.
In Transaction Manager Communication, select the Allow Inbound and Allow Outbound check boxes.
I had a store procedure that call another store Procedure in "linked server".when I execute it in ssms it was ok,but when I call it in application(By Entity Framework),I got this error.
This article helped me and I used this script:
EXEC sp_serveroption #server = 'LinkedServer IP or Name',#optname = 'remote proc transaction promotion', #optvalue = 'false' ;
for more detail look at this:
Linked server : The partner transaction manager has disabled its support for remote/network transactions
In my scenario, the exception was being thrown because I was trying to create a new connection instance within a TransactionScope on an already existing connection:
Example:
void someFunction()
{
using (var db = new DBContext(GetConnectionString()))
{
using (var transaction = new TransactionScope(TransactionScopeOption.Required, new TransactionOptions { IsolationLevel = System.Transactions.IsolationLevel.ReadUncommitted }))
{
someOtherFunction(); // This function opens a new connection within this transaction, causing the exception.
}
}
}
void someOtherFunction()
{
using (var db = new DBContext(GetConnectionString()))
{
db.Whatever // <- Exception.
}
}
I was getting this issue intermittently, I had followed the instructions here and very similar ones elsewhere. All was configured correctly.
This page: http://sysadminwebsite.wordpress.com/2012/05/29/9/ helped me find the problem.
Basically I had duplicate CID's for the MSDTC across both servers. HKEY_CLASSES_ROOT\CID
See: http://msdn.microsoft.com/en-us/library/aa561924.aspx section Ensure that MSDTC is assigned a unique CID value
I am working with virtual servers and our server team likes to use the same image for every server. It's a simple fix and we didn't need a restart. But the DTC service did need setting to Automatic startup and did need to be started after the re-install.
Comment from answer: "make sure you use the same open connection for all the database calls inside the transaction. – Magnus"
Our users are stored in a separate db from the data I was working with in the transactions. Opening the db connection to get the user was causing this error for me. Moving the other db connection and user lookup outside of the transaction scope fixed the error.
I post the below solution here because after some searching this is where I landed, so other may too. I was trying to use EF 6 to call a stored procedure, but had a similar error because the stored procedure had a linked server being utilized.
The operation could not be performed because OLE DB provider _ for linked server _ was unable to begin a distributed transaction
The partner transaction manager has disabled its support for remote/network transactions*
Jumping over to SQL Client did fix my issue, which also confirmed for me that it was an EF thing.
EF model generated method based attempt:
db.SomeStoredProcedure();
ExecuteSqlCommand based attempt:
db.Database.ExecuteSqlCommand("exec [SomeDB].[dbo].[SomeStoredProcedure]");
With:
var connectionString = db.Database.Connection.ConnectionString;
var connection = new System.Data.SqlClient.SqlConnection(connectionString);
var cmd = connection.CreateCommand();
cmd.CommandText = "exec [SomeDB].[dbo].[SomeStoredProcedure]";
connection.Open();
var result = cmd.ExecuteNonQuery();
That code can be shortened, but I think that version is slightly more convenient for debugging and stepping through.
I don't believe that Sql Client is necessarily a preferred choice, but I felt this was at least worth sharing if anyone else having similar problems gets landed here by google.
The above Code is C#, but the concept of trying to switch over to Sql Client still applies. At the very least it will be diagnostic to attempt to do so.
I was having this issue with a linked server in SSMS while trying to create a stored procedure.
On the linked server, I changed the server option "Enable Promotion on Distributed Transaction" to False.
Screenshot of Server Options
If you could not find Local DTC in the component services try to run this PowerShell script first:
$DTCSettings = #(
"NetworkDtcAccess", # Network DTC Access
"NetworkDtcAccessClients", # Allow Remote Clients ( Client and Administration)
"NetworkDtcAccessAdmin", # Allow Remote Administration ( Client and Administration)
"NetworkDtcAccessTransactions", # (Transaction Manager Communication )
"NetworkDtcAccessInbound", # Allow Inbound (Transaction Manager Communication )
"NetworkDtcAccessOutbound" , # Allow Outbound (Transaction Manager Communication )
"XaTransactions", # Enable XA Transactions
"LuTransactions" # Enable SNA LU 6.2 Transactions
)
foreach($setting in $DTCSettings)
{
Set-ItemProperty -Path HKLM:\Software\Microsoft\MSDTC\Security -Name $setting -Value 1
}
Restart-Service msdtc
And it appears!
Source: The partner transaction manager has disabled its support for remote/network transactions
In case others have the same issue:
I had a similar error happening. turned out I was wrapping several SQL statements in a transactions, where one of them executed on a linked server (Merge statement in an EXEC(...) AT Server statement). I resolved the issue by opening a separate connection to the linked server, encapsulating that statement in a try...catch then abort the transaction on the original connection in case the catch is tripped.
I had the same error message. For me changing pooling=False to ;pooling=true;Max Pool Size=200 in the connection string fixed the problem.
In normal condition, I can add schemas in the dbml file to empty database with code below.
But now when I run this code, I take the error "Cannot drop database "test" because it is currently in use." How can I do it?
Dim db As New UI_Class.UIData
If db.DatabaseExists Then
db.DeleteDatabase()
End If
db.CreateDatabase()
It might happen as your SQL Server Management Studio (SSMS) must be holding it.
Most likely something is connected to the db.
Common causes are:
Some other tool connected
Trying to delete the database you connected to.
Another user connected to the db.