Transaction (Process ID) was deadlocked

 The error message "Transaction (Process ID) was deadlocked" typically occurs in a database system, such as SQL Server, when two or more transactions are trying to access the same resources simultaneously, but in a way that leads to a deadlock. This means each transaction is waiting for the other to release a resource, creating a situation where none of them can proceed.

Here are steps to troubleshoot and resolve this issue:

1. Identify the Deadlock:

• SQL Server Profiler: Use SQL Server Profiler to trace deadlocks. You can configure it to capture deadlock graphs.
• Extended Events: Use Extended Events in SQL Server to capture deadlock information. This can be more efficient than using the Profiler.
• System Health Session: SQL Server includes a default system health session that captures deadlock information. You can query it to find details about deadlocks.

2. Analyze the Deadlock Graph:

• Look at the deadlock graph to understand which transactions and resources are involved.
• Determine the sequence of locks that lead to the deadlock.

3. Review and Optimize Queries:

• Indexes: Ensure proper indexing to reduce lock contention.
• Query Design: Optimize queries to be more efficient and reduce the duration of locks.
• Transaction Scope: Minimize the scope and duration of transactions to lower the likelihood of deadlocks.

4. Lock Hints and Isolation Levels:

• Lock Hints: Use lock hints (e.g., NOLOCK, ROWLOCK) where appropriate to control locking behavior.
• Isolation Levels: Adjust transaction isolation levels. For instance, using READ COMMITTED SNAPSHOT can reduce locking and blocking.

5. Retry Logic:

• Implement retry logic in your application to handle deadlocks gracefully. When a deadlock occurs, retry the transaction after a short delay.

6. Database Design:

• Ensure the database schema is designed to minimize locking conflicts. For example, properly normalizing tables and using appropriate data types.

Example: Implementing Retry Logic in T-SQL

DECLARE @retry INT = 0;
DECLARE @max_retries INT = 3;
DECLARE @delay INT = 500; -- milliseconds

WHILE @retry < @max_retries
BEGIN
    BEGIN TRY
        BEGIN TRANSACTION;

        -- Your SQL operations here

        COMMIT TRANSACTION;
        BREAK; -- Exit the loop if the transaction is successful
    END TRY
    BEGIN CATCH
        IF ERROR_NUMBER() = 1205 -- Deadlock error number
        BEGIN
            SET @retry = @retry + 1;
            IF @retry < @max_retries
            BEGIN
                WAITFOR DELAY '00:00:00.500'; -- Wait for 500 milliseconds before retrying
            END
            ELSE
            BEGIN
                THROW; -- Raise the error if max retries reached
            END
        END
        ELSE
        BEGIN
            THROW; -- Raise the error if it's not a deadlock
        END
    END CATCH
END

Example: Adjusting Isolation Levels

SET TRANSACTION ISOLATION LEVEL READ COMMITTED;
BEGIN TRANSACTION;

-- Your SQL operations here

COMMIT TRANSACTION;

Example: Using Extended Events to Capture Deadlocks

CREATE EVENT SESSION [CaptureDeadlocks] ON SERVER
ADD EVENT sqlserver.lock_deadlock
ADD TARGET package0.event_file(SET filename=N'C:\Path\To\Your\File\DeadlockCapture.xel', max_file_size=(5))
WITH (MAX_MEMORY=4096 KB, EVENT_RETENTION_MODE=ALLOW_SINGLE_EVENT_LOSS, MAX_DISPATCH_LATENCY=30 SECONDS, MAX_EVENT_SIZE=0 KB, MEMORY_PARTITION_MODE=NONE, TRACK_CAUSALITY=OFF, STARTUP_STATE=OFF);
GO

ALTER EVENT SESSION [CaptureDeadlocks] ON SERVER STATE = START;
GO

By following these steps and using the appropriate tools and techniques, you can effectively troubleshoot and resolve deadlock issues in your database system.

Could not allocate space for object

 The error "Could not allocate space for object" typically indicates that the database has run out of space in the filegroup or the file where the object (table, index, etc.) resides. This can happen due to several reasons such as the filegroup being full, the database reaching its maximum size, or the disk being out of space.

Here are steps to troubleshoot and resolve this issue:

1. Check Disk Space:

   • Ensure that there is enough free space on the disk where the database files are stored. If the disk is full, free up some space.

2. Check Database File Sizes:

• Verify the current size and the maximum size of the database files. Use the following query to check the size of the database files:

USE YourDatabaseName;
GO
EXEC sp_helpfile;

    3. Increase Database File Size:

• If the database file has reached its maximum size, you can increase its size or set it to auto-grow. Use the following command to increase the size:

ALTER DATABASE YourDatabaseName
MODIFY FILE (NAME = 'YourLogicalFileName', SIZE = new_size_in_MB);

To set the file to auto-grow, use:

ALTER DATABASE YourDatabaseName
MODIFY FILE (NAME = 'YourLogicalFileName', FILEGROWTH = growth_increment_in_MB);

  4.  Add a New File to the Filegroup:

• If the filegroup is full, you can add a new file to the filegroup:

ALTER DATABASE YourDatabaseName
ADD FILE (
    NAME = 'NewFileName',
    FILENAME = 'path_to_new_file',
    SIZE = initial_size_in_MB,
    FILEGROWTH = growth_increment_in_MB
) TO FILEGROUP 'YourFileGroupName';

  5. Shrinking Files:

• If there is unused space within the database files, you can reclaim it by shrinking the files. However, use this option with caution as it can lead to fragmentation.

DBCC SHRINKFILE (YourLogicalFileName, target_size_in_MB);

  6. Monitor and Maintenance:

• Regularly monitor the database size and growth patterns to anticipate and manage space issues before they become critical.