In go, I open a sqlite3 database using the mattn/go-sqlite3 module. I set the database journalling mode to WAL immediately after opening using a PRAGMA journal_mode=WAL.
However, if I try to open the database from a second process while the first is running, the second cannot open it and instead gets the "database is locked" error. This happens even if I did not perform any transactions.
The connection string I am using is:
"file:mydbfile.db?cache=shared&mode=rwc"
(I intend to answer my own question, since it took a long time to debug)
If you want to enable journal_mode=WAL, you should add it to the connection string:
"file:mydbfile.db?cache=shared&mode=rwc&_journal_mode=WAL"
As part of opening the database, go-sqlite3 will execute PRAGMA statements to set various defaults. One of these defaults is setting the journal_mode=DELETE. However, if another process has the database opened, the mode cannot be changed back to DELETE. Executing this statement fails with "database is locked" and so you will see the open operation fail with that error.
The complete list of connection string parameters is listed at https://github.com/mattn/go-sqlite3
Related
I am writing a wrapper shell or perl script which does open an oracle session using sqlplus and then execute some sql files by scanning a directory. So as part of this , lets say if we have multiple sql files in a directory,
for eg: first.sql,second.sql,third.sql
I am planning to create a single file(AllSqlFilesInDirectory.sql) with below content.
>cat AllSqlFilesInDirectory.sql
#first.sql
#second.sql
#third.sql
>
Now I am planning to run the file AllSqlFilesInDirectory.sql by opening an oracle sqlplus session.
After executing, I am planning to come out of the oracle sqlplus session and I am planning to search for any errors in the log file.
If there are any errors, I would like to execute rollback. But I think as I am out of that sqlplus session, rollback is not possible. I am just concerned about the DML statements that were executed as part of those multiple sql files in the directory.
So I have these doubts
Can I simply ignore and not be concerned about rollback at all
Can I do the rollback for a session which was already closed?
If above is valid, then how can do it?
Can I simply ignore and not be concerned about rollback at all
That's a business question you'd have to answer. If you want the changes to be rolled back if there is an error, you'd need to do a rollback.
Can I do the rollback for a session which was already closed?
As a practical matter, probably not. Technically, you can using flashback transaction backout but that is generally way more complexity that you'd normally want to deal with.
If above is valid, then how can do it?
Rather than writing to a log file and parsing the log file to determine if there were any errors, it is most likely vastly easier to simply put a
whenever sqlerror exit rollback
at the top of your script. That tells SQL*Plus to rollback the transaction and exit whenever an error is encountered. You don't have to write logic to parse the log file.
Whenever sqlerror documentation
I am creating an MVC application using Oracle's Entity Framework, and am writing a bit of code to iterate through all relevant DBLinks and testing them out, returning a grid of results (success/fail). My problem is that after using the fourth DBLink, I get an error "ORA-02020: too many database links in use".
I have tried to explicitly close each DBLink after using it ("alter session close database link LinkName"), but I then receive an error "ORA-02080: database link is in use".
I have tried issuing "COMMIT" statement before attempting to close the DBLink, but that doesn't change the error ("database link is in use").
I have tried to closing the database connection, but I still receive the "database link is in use" error when I create a new connection and try to close the DBLink.
Unfortunately, increasing the number of DBLinks available (open_links, open_links_per_instance) is not an option.
Has anyone seen this with Entity Framework and discovered a solution? Does anyone have any ideas of what else to try?
VICTORY! I found that if I set "Pooling=false" in my connection string, then this error goes away in all of the offending scenarios. This is viable for me since this is just used to test the DBLinks on demand, so I can safely turn off pooling in this scenario. Thanks so much for your responses. I was ready to turn in the towel and admit defeat
To see how many db links are open i syour session use the GV$DBLINK view
select DB_LINK from GV$DBLINK;
DB_LI
-----
LEDRP
YDO
To close a db link you must do two things.
First commit or rollback the transaction. Note that even if you do not change anything a transaction is open due to the use of the DB LINK.
Second you must CLOSE DATABASE LINK using the ALTER SESSION statement.
rollback;
ALTER SESSION CLOSE DATABASE LINK LEDRP;
You see, that link is closed and appears not in the view:
select DB_LINK from GV$DBLINK;
DB_LI
-----
YDOV
I use datagrip to move some data from a mysql installation to another postresql-database.
That worked for 3 other tables like a charm. The next one, over 500.000 rows big, could not be imported.
I use the function "Copy Table To... (F5)".
This is the log.
16:28 Connected
16:30 user#localhost: tmp_post imported to forum_post: 1999 rows (1m
58s 206ms)
16:30 Can't save current transaction state. Check connection and
database settings and try again.
For other errors like wrong data types, null data on not null columns, a very helpful log is created. But not now.
The problem is also relevant when using the database plugin for IntelliJ-based IDEs, not only DataGrip
The simplest way to solve the issue is just to add "prepareThreshold=0" to your connection string as in this answer:
jdbc:postgresql://ip:port/db_name?prepareThreshold=0
Or, for example, if you a using several settings in the connection string:
jdbc:postgresql://hostmaster.com:6432,hostsecond.com:6432/dbName?&targetServerType=master&prepareThreshold=0
It's a well-known problem when connecting to the PostgreSQL server via PgBouncer rather than a problem with IntelliJ itself. When loading massive data to the database IntelliJ splits data into chunks and loads them sequentially, each time executing the query and committing the data. By default, PostgreSQL starts using server-side prepared statements after 5 execution of a query.
The driver uses server side prepared statements by default when
PreparedStatement API is used. In order to get to server-side prepare,
you need to execute the query 5 times (that can be configured via
prepareThreshold connection property). An internal counter keeps track
of how many times the statement has been executed and when it reaches
the threshold it will start to use server side prepared statements.
Probably your PgBouncer runs with transaction pooling and the latest version of PbBouncer doesn't support prepared statements with transaction pooling.
How to use prepared statements with transaction pooling?
To make prepared statements work in this mode would need PgBouncer to
keep track of them internally, which it does not do. So the only way
to keep using PgBouncer in this mode is to disable prepared statements
in the client
You can verify that the issue is indeed because of the incorrect use of prepared statements with the pgbouncer via viewing IntelliJ log files. For that go to Help -> Show Log in Explorer, and search for "org.postgresql.util.PSQLException: ERROR: prepared statement" exception.
2022-04-08 12:32:56,484 [693272684] WARN - j.database.dbimport.ImportHead - ERROR: prepared statement "S_3649" does not exist
java.sql.SQLException: ERROR: prepared statement "S_3649" does not exist
at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2440)
at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2183)
at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:308)
at org.postgresql.jdbc.PgConnection.executeTransactionCommand(PgConnection.java:755)
at org.postgresql.jdbc.PgConnection.commit(PgConnection.java:777)
I'm currently troubleshooting a VB6 application that sporadically comes up with the following error:
[Oracle][ODBC][Ora]ORA-01013: user requested cancel of current operation
All of the research I've done on this error states that it is either an actual request for cancellation by the user or a timeout. It can't be a request for cancellation because the input is coming in from an automated source, so it must be a timeout. One thing I read online was to un-check the query timeout checkbox in the DSN configuration box but my program uses a DSN-less connection to the database, which is an Oracle 10g database.
There are several queries in this program but it always fails on one query in particular, however I can't reproduce the error in a test environment using all of the same input to the program that caused the error in the first place.
A co-worker of mine suggested doing a rollback after each query even though the queries are read only because some kind of buffer might be getting filled up or something of the like, but this didn't work. At this point I don't even know how to continue troubleshooting it because I can't reproduce the error. If someone could give me any idea of what is going on and how to fix the problem I'd greatly appreciate it. Thanks in advance!
All of the options that you can choose when setting up a DSN can be specified in the connection string if you are using a DSN-less connection. If you want to disable query timeouts, you would add
QTO=F
to the connection string. So your new connection string would be something like
DRIVER={Oracle ODBC Driver};UID=Kotzwinkle;PWD=whatever;DBQ=instl_alias;QTO=F;
I've got a load-balanced (not using Session state) ASP.Net 2.0 app on IIS5 running back to a single Oracle 10g server, using version 10.1.0.301 of the ODAC/ODP.Net drivers. After a long period of inactivity (a few hours), the application, seemingly randomly, will throw an Oracle exception:
Exception: ORA-03113: end-of-file on communication channel at
Oracle.DataAccess.Client.OracleException.HandleErrorHelper(Int32
errCode, OracleConnection conn, IntPtr opsErrCtx, OpoSqlValCtx*
pOpoSqlValCtx, Object src, String procedure) at
Oracle.DataAccess.Client.OracleCommand.ExecuteReader(Boolean requery,
Boolean fillRequest, CommandBehavior behavior) at
Oracle.DataAccess.Client.OracleCommand.System.Data.IDbCommand.ExecuteReader()
...Oracle portion of the stack ends here...
We are creating new connections on every request, have the open & close wrapped in a try/catch/finally to ensure proper connection closure, and the whole thing is wrapped in a using (OracleConnection yadayada) {...} block. This problem does not appear linked to the restart of the ASP.Net application after being spun down for inactivity.
We have yet to reproduce the problem ourselves. Thoughts, prayers, help?
More: Checked with IT, the firewall isn't set to kill connections between those servers.
ORA-03113: end-of-file on communication channel
Is the database letting you know that the network connection is no more. This could be because:
A network issue - faulty connection, or firewall issue
The server process on the database that is servicing you died unexpectedly.
For 1) (firewall) search tahiti.oracle.com for SQLNET.EXPIRE_TIME. This is a sqlnet.ora parameter that will regularly send a network packet at a configurable interval ie: setting this will make the firewall believe that the connection is live.
For 1) (network) speak to your network admin (connection could be unreliable)
For 2) Check the alert.log for errors. If the server process failed there will be an error message. Also a trace file will have been written to enable support to identify the issue. The error message will reference the trace file.
Support issues can be raised at metalink.oracle.com with a suitable Customer Service Identifier (CSI)
Add Validate Connection=true to your connection string.
Look at this blog to find more about.
DETAILS:
After OracleConnection.Close() the real database connection does not terminate. The connection object is put back in connection pool. The use of connection pool is implicit by ODP.NET. If you create a new connection you get one of the pool. If this connection is "yet open" the OracleConnection.Open() method does not really creates a new connection. If the real connection is broken (for any reason) you get a failure on first select, update, insert or delete.
With Validate Connection the real connection is validated in Open() method.
Check that there isn't a firewall that is ending the connection after certain period of time (this was the cause of a similar problem we had)
end-of-file on communication channel:
One of the course of this error is due to database fail to write the log when its in the stage of opening;
Solution check the database if its running in ARCHIVELOG or NOARCHIVELOG
to check use
select log_mode from v$database;
if its on ARCHIVELOG try to change into NOARCHIVELOG
by using sqlplus
startup mount
alter database noarchivelog;
alter database open;
if it works for this
Then you can adjust your flashrecovery area its possibly that your flashrecovery area is full
-> then after confirm that your flashrecovery area has the space you can alter your database into the ARCHIVELOG
This error message can be thrown in the application logs when the actual issue is that the oracle database server ran out of space.
After correcting the space issue, this particular error message disappeared.
You could try this registry hack:
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters]
"DeadGWDetectDefault"=dword:00000001
"KeepAliveTime"=dword:00120000
If it works, just keep increasing the KeepAliveTime. It is currently set for 2 minutes.
The article previously mentioned is good. http://forums.oracle.com/forums/thread.jspa?threadID=191750 (as far as it goes)
If this is not something that runs frequently (don't do it on your home page), you can turn off connection pooling.
There is one other "gotcha" that is not mentioned in the article. If the first thing you try to do with the connection is call a stored procedure, ODP will HANG!!!! You will not get back an error condition to manage, just a full bore HANG! The only way to fix it is to turn OFF connection pooling. Once we did that, all issues went away.
Pooling is good in some situations, but at the cost of increased complexity around the first statement of every connection.
If the error handling approach is so good, why don't they make it an option for ODP to handle it for us????
//First start the database in mount mode
startup mount
//Disable archivelog
alter database noarchivelog
//Then put db in open
alter database open