Firedac phys sqlite error database is locked

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Firedac phys sqlite error database is locked
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Delphi: Database is locked (SQLite)
2 Answers 2
The pure way (using parameters)
The dirty way (building SQL)
Помогите начать работу с Oracle
Вопрос
sulion
sulion
How to solve [FireDAC][Phys][SQLite] ERROR: unable to open database file, When app is installed in programFiles?
1 Answer 1

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Delphi Xe5 firedac Database locked error with SQLite database

I am trying to create a simple object to handle all my database related functions. I have a functions to return a dataset or to execute a command. Now when i call this from my program I am able to fetch records using Execute_Dataset and it works fine but when i do an changes and execute a command by calling Execute_Command i get an error «database is locked» when the commit transaction is called. I have tried everything that i could be it still happens. Can someone put some light into what i am doing wrong and how i can prevent this from happening.

3 Answers 3

Try setting the Connection’s properties SharedCache to ‘False’ and LockingMode to ‘Normal’.

The default value for the connection’s locking mode is ‘exclusive’ which can cause this problem. You can do this by right clicking on your Connection-Component (on the form) and choosing ConnectionEditor (I’m not quite sure, if that’s the right English word for it, but it should be called something like that) and then setting these values.

Alternatively you can set these properties in sourcecode:

I’m not sure that this is the best way to solve this problem. There might be a better solution to this.

Because other connection exist. Check connection component in datamodule MyFDConnection.Connected:=False;

Sharedcache = false is indeed the best way to solve this problem. The components already support designtime connections.

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Delphi: Database is locked (SQLite)

I am facing two problems.

(1) When I try to write to a Database (SQLite) by using Delphi XE6, I always get the Database is locked error message. I am certain that I close the database everytime I access it by using the command FDConnection1.Close;

(2) How do I INSERT INTO a table from incoming parameters? I have the following incoming parameters

and tried to write into the table with the following SQL command:

but it does not seem to work.

The following is the complete procedure I am having trouble with

Any hints will be very appreciated. Thanks in advance.

2 Answers 2

There are two techniques to executing a dynamic SQL statement. But I’ll use a shorter SQL, to concentrate on the logic:

The pure way (using parameters)

The dirty way (building SQL)

The differences are significant. The dirty way exposes you to SQL injection problems (as in most other languages, when you build SQL dinamically but without parameters). This could be or not be a problem for you. If you know that the procedure is only called privately by your own code, and that those procedure parameter values can only contain good values. or if you do some good parameter checking before building and executing your SQL. then you are safe.

But if you do it with parameters (the pure way) you are automatically protected from SQL injection, as the SQL statement is validated by the engine, without knowing the parameter values. So the SQL statement structure is known by the engine and cannot be altered by the actual values.

Another consideration is how frequently you will execute that INSERT statement. The pure way allows you to prepare the query ONCE, and execute it MANY TIMES with different parameter values (you must not destroy the query object, nor change the SQL property, and you must call the Prepare method once). If you run it frequently within a loop then it can be more efficient than building the SQL many times the dirty way. OTOH if you just need to insert one single row, it may pose a bit more overhead.

As an aside. CL is right. those values should not be strings. Keep in mind that the Parameter object has many properties to handle different data types:

If you don’t use parameters, then things get difficult. The QuoteStr function is good for strings, but if you want to burn dates and currencies and other value types directly in your SQL you have to know what you are doing. You may encounter many different problems. locale specific or format settings that are not good for comunicating with your server, which may be on the opposite end of the world, or may just not be able to read values formatted that way. You may have to handle engine specific formatting and conversion problems.

If you do use parameters, then FireDAC should take care of all this for you 😉

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Помогите начать работу с Oracle

Ответ от sulion,
28 мая, 2019

Вопрос

sulion

Коллеги, добрый день!

Вопрос на засыпку — помогите пожалуйста, чего мне не хватает для успешного запуска?

Список dll файликов прикрепляю внизу письма, Oracle 12.2 клиент стоит, PL/SQL Developer 12 использую каждый день

Из хорошего — FireDAC Explorer успешно видит все нужные мне БД — и таблицы, и пакеты и т.д.

В Delphi XE7 приложение работало успешно. Delphi 10.2.3 подчёркивает два модуля. Если эти два модуля закомментарить, то — компилирует успешно, но не может подцепиться ни к одной БД Oracle

Создал пустое приложение, в него положил TFDConnection, драйвер Oracle он не видит

Что уже пробовал:

Вчера поставил все dll. Сегодня поставил Delphi 10.3.1 Architect Trial (на месяц), в нём проблема воспроизводится. Ещё раз переустановил драйвер Oracle.

Что ещё можно сделать?

Обещанный список dll:

oci.dll
ocijdbc12.dll
ocijdbc12.sym
ociw32.dll
ociw32.sym
ojdbc8.jar
oramysql12.dll
oramysql12.sym
orannzsbb12.dll
orannzsbb12.sym
oraocci12.dll
oraocci12.sym
oraocci12d.dll
oraocci12d.sym
oraociei12.dll
oraociei12.sym
oraons.dll
orasql12.dll
orasql12.sym

Изменено 31 мая, 2019 пользователем sulion

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How to solve [FireDAC][Phys][SQLite] ERROR: unable to open database file, When app is installed in programFiles?

I developed a tool using Firedac with the database as SQLite.

after finishing the project and making an installer (InnoSetup) I get an error

[FireDAC][Phys][SQLite] ERROR: unable to open database file

when I launch the app (double click).

This is the connection parameters I use

I read somewhere (do not remember the page I was in) that SQLite engine requires full lock on the directory that it wants to write to. and this is the problem. How ever I run the tool as invoker and my account is an admin so that is not a problem. Also I have the same tool written in c# and this problem never occurs.

Solutions I found:

Run the tool as administrator
Do not Install the tool in ProgramFiles directory

I really don’t like these solutions. and would like to run my tool from program Files directory as it is part of a bigger project.

Note: The database file is in programdata directory. It is created by the tool (this works).

Edit: I just tried putting the DB file in C:UsersNacereddineAppDataRoamingMyTool And I still have the same problem when the tool is installed in C:Program Files (x86)MyTool

This how I create the DB file

Note: I do not know if this makes any difference but the Db file is encrypted.

1 Answer 1

Sorry for the trouble folks.

The problem was that we had a Localization db file installed with the tool in ProgramFiles.

What made me exclude that from my investigation is that, when opening this file I set the OpenMode to ReadOnly

but as I said before in my question SQLite engine requires full access to the folder containing the db file so it preforms a lock on it (still did not find the page I read this on).

I checked this by playing around with open modes and debugging the tool each time. once I changed the permissions of both the file and the directory the error was gone.

at the end I decided to move the localization file to the programData directory with the main db file and all is well.

I realized (Thank you for this @Ken and @David) that the programData directory also requires admin permissions to write to, and therefore I will move the db files to a more appropriate dir (i.e Users).

What is useful from this problem is that even if you connect to the Sqlite db file with OpenMode=ReadOnly , you still need write access for the path to that file.

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  function TConnectionManager.Execute_Dataset(const ASql: string; const AParams:
      array of variant; out VDataset: TDataset; const ATrn_Name: string): Boolean;
  var
    lTrn: TFDTransaction;
    lQry: TFDQuery;
  begin
    Result := True;
    lTrn:= TFDTransaction.Create (Self);
    try
      lTrn.Connection := FConnection;
      lTrn.StartTransaction;
      lQry := TFDQuery.Create (Self);
      lQry.Connection := FConnection;
      lQry.Transaction := lTrn;
      try
        if Length (AParams) > 0
        then lQry.Open (ASql, AParams)
        else lQry.Open (ASql);
        VDataset := lQry;
        Result := True;
        { Commit transaction if started within the procedure }
        lTrn.Commit;
      except
        on e:Exception
        do begin
           { Rollback transaction if started within the procedure }
           lTrn.Rollback;
           lQry.DisposeOf;
           //log
           raise;
        end;
      end;
    finally
      lTrn.DisposeOf;
    end;
  end;



 procedure TConnectionManager.Execute_Command(const ASql: string; const AParams:
      array of variant; const ATrn_Name: string);
  var
    lTrn: TFDTransaction;
    lQry: TFDQuery;
  begin
    lTrn:= TFDTransaction.Create (Self);
    try
      lTrn.Connection := FConnection;
      lTrn.StartTransaction;
      lQry := TFDQuery.Create (Self);
      lQry.Connection := FConnection;
      lQry.Transaction := lTrn;
      try
        { Execute command }
        if Length (AParams) > 0
        then lQry.ExecSQL (ASql, AParams)
        else lQry.ExecSQL (ASql);
        { Commit transaction if started within the procedure }
        lTrn.Commit;
      except
        on e:Exception
        do begin
           { Rollback transaction if started within the procedure }
           lTrn.Rollback;
           //log
           raise;
        end;
      end;
    finally
      lQry.DisposeOf;
      lTrn.DisposeOf;
    end;
  end;

Thanks

Dreamwalker

3,0324 gold badges30 silver badges60 bronze badges

asked Apr 9, 2014 at 22:03

Try setting the Connection’s properties SharedCache to ‘False’ and LockingMode to ‘Normal’.

The default value for the connection’s locking mode is ‘exclusive’ which can cause this problem. You can do this by right clicking on your Connection-Component (on the form) and choosing ConnectionEditor (I’m not quite sure, if that’s the right English word for it, but it should be called something like that) and then setting these values.

Alternatively you can set these properties in sourcecode:

connection.Params.Add('SharedCache=False');
connection.Params.Add('LockingMode=Normal');

I’m not sure that this is the best way to solve this problem. There might be a better solution to this.

Michael

3,2905 gold badges23 silver badges36 bronze badges

answered Mar 16, 2015 at 8:53

Because other connection exist. Check connection component in datamodule
MyFDConnection.Connected:=False;

answered Mar 7, 2019 at 12:44

CfonCfon

2152 silver badges9 bronze badges

Sharedcache = false is indeed the best way to solve this problem. The components already support designtime connections.

marc_s

722k173 gold badges1320 silver badges1443 bronze badges

answered Aug 16, 2019 at 10:43

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Теги: delphi rio

Установите, как показано:

Код. Чтобы

    FDQuery1.Close;
    FDQuery1.SQL.Clear;
    FDQuery1.SQL.Add('select * from photos');
    FDQuery1.Active:= true;
    for icount := 0 to tmpstr.Count - 1 do
    begin
       FDQuery1.Insert;
       FDQuery1.FieldByName('path').AsString:=tmpstr.Strings[icount];
       FDQuery1.Post;
    end;

результат.

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database is locked
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асинхронный
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unsatisfiedlinkerror

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Facing SQLite database is locked error code 5? Having difficulties while performing operations or transactions in the database. Do not worry. You’ll get to know how to resolve this error using both manual and alternate methods.

SQLite is a database management system which is operated in C language programming library. If you are an SQLite user, you must have come across the error Database is locked. It is one of the frequent errors.

Causes for SQLite Error Database is locked code 5

Usually, this error code appears whenever an SQLite user intends to perform two inappropriate transactions or operations in a database on the same data connection and on the same other details.

The error message indicates that a similar operation can not be performed as there is an encounter with the transaction using the same database connection or a different database connection using shared cache.

Various scenarios of SQLite error database is locked

Some of the situations and scenarios under which there are chances of occurrence of error code 5 SQLite database is locked are as:

When you use a table to write and on which the SELECT operations is previously activated.
The database gets locked in a situation when you try to DROP or CREATE an index or table while SELECT statement is still in a pending state. The main reason behind it is the misconception of the users that if the Sqlite3_() returns the SQLITE_DONE value, the SELECT statement is finished. However, there is a different scenario because the SELECT statement is not considered to be completed until Sqlite3_reset() or Sqlite3_finalize() are called.
When you try two SELECT operations on same table at same time in an application having multiple threads and SQLite is not allowed for the same, there are chances that the database may get locked.

Manual method to fix SQLite error Database is locked code 5

One of the best way to resolve this SQLite database is locked error is to create a database backup having no locks on it. After doing that, you need to replace the original database with its backed up copy. You can go through the below scripts to perform the same task. Here, .x.Sqlite is meant as Sqlite database file.

$Sqlite3 .x.Sqlite

Sqlite> .backup main backup.Sqlite

Sqlite> .exit

In the same directory, you’ll have backup file named as backup.Sqlite. You need to replace your old database file with the new backup file copy of the SQLite database. The backup file is not locked up and hence the SQLite error database is locked code 5 will not appear.

$mv .x.Sqlite old.Sqlite

$mv backup.Sqlite .x.Sqlite

Once the above script gets successfully executed, you can use your database with full access. Ensure that both read and write operations are allowed to run on the database. After that, you can delete the old file having SQLite database.

You may also read: Repair SQLite Database

Alternative to resolve SQLite database is locked error

If you are having difficulty in manual methods or using manual method the problem doesn’t get resolved, you can use the alternate method of using an SQLite Database Recovery software. It successfully recovers all the SQLite database and fixes the corruptions in the database created by both SQLite2 and SQLite3. Also, it is an efficient tool that is built up with advanced algorithm. It successfully fixes the SQLite error code 5 database is locked.

Conclusion

In this technical article, we have come across the SQLite error Database is locked, reasons behind its occurrence and the possible manual and expert methods to resolve this particular error. Go through these solutions as per your choice. Hope the article helps.

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