Snippet Name: Long_Running_Transaction_Troubleshooting
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Created Date: 2025-06-16 13:12:46
Last Modified Date: 2025-05-31 10:32:06
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Title: Long Running Transaction Troubleshooting
Author: user
In SQL server2019, i have an ongoing, long running transaction. i know the spid /sesisonid happens to be 545.
Author: ChatGPT
Since you know the **SPID (Session ID)** of the long-running transaction (**545**), you can investigate it further and decide whether to **wait, kill, or troubleshoot**. Here???s how you can proceed:
### 1?????? **Check Transaction Details**
Run the following query to get details about the transaction, including **status, blocking information, start time, and duration**:
```sql
SELECT
r.session_id,
r.status,
r.blocking_session_id,
r.wait_type,
r.wait_time,
r.wait_resource,
r.percent_complete,
r.cpu_time,
r.total_elapsed_time,
r.reads,
r.writes,
r.logical_reads,
r.program_name,
r.host_name,
r.login_name,
t.transaction_id,
t.transaction_begin_time
FROM sys.dm_exec_requests r
JOIN sys.dm_tran_active_transactions t ON r.transaction_id = t.transaction_id
WHERE r.session_id = 545;
```
### 2?????? **Check SQL Text of the Transaction**
To see what query is running under SPID **545**, execute:
```sql
SELECT
r.session_id,
r.status,
r.command,
t.text AS sql_text
FROM sys.dm_exec_requests r
CROSS APPLY sys.dm_exec_sql_text(r.sql_handle) t
WHERE r.session_id = 545;
```
### 3?????? **Check Locks Held by the Session**
To see what resources the session is locking (which may cause blocking):
```sql
SELECT
request_session_id AS SessionID,
resource_type,
resource_description,
request_mode,
request_status
FROM sys.dm_tran_locks
WHERE request_session_id = 545;
```
### 4?????? **Check Blocking (If Any)**
If **SPID 545 is blocked** or **is blocking others**, this will show the blocking chain:
```sql
SELECT
blocking_session_id AS BlockingSPID,
session_id AS BlockedSPID,
wait_type,
wait_time,
wait_resource
FROM sys.dm_exec_requests
WHERE blocking_session_id <> 0;
```
### 5?????? **Check Open Transactions for SPID**
If the session has open transactions, you can check them:
```sql
DBCC OPENTRAN;
```
or
```sql
SELECT
session_id,
transaction_id,
database_id,
database_transaction_begin_time
FROM sys.dm_tran_database_transactions
WHERE session_id = 545;
```
---
### ???? **KILL the Session (if needed)**
If the session is stuck or causing blocking, you can **kill it**:
```sql
KILL 545;
```
If the rollback takes too long, monitor it with:
```sql
SELECT session_id, percent_complete, estimated_completion_time
FROM sys.dm_exec_requests
WHERE session_id = 545;
```
---
### ???? **Next Steps**
- If the session is waiting on **I/O, CPU, or locks**, troubleshoot the cause.
- If it???s a **blocking session**, resolve the root blocker instead of killing.
- If it???s a **long-running query**, evaluate if **query tuning or indexing** can help.
- If it???s **stuck due to deadlock**, check `sys.dm_tran_locks` and resolve it accordingly.
Would you like me to help **analyze the execution plan or optimize the query**? ????
Author: user
is it possible to estimate the amount of data pending inhte log for the transaciton, or the tables that are members of the transaction?
Author: ChatGPT
Yes! You can estimate the **amount of data pending in the log** for the transaction and identify the **tables involved**. Here???s how:
---
### **1?????? Check Log Usage for the Transaction**
To estimate the log space used by the ongoing transaction (SPID **545**), run:
```sql
SELECT
s.session_id,
t.transaction_id,
t.database_id,
d.name AS database_name,
t.database_transaction_log_bytes_used / 1024.0 AS LogKB_Used,
t.database_transaction_log_bytes_reserved / 1024.0 AS LogKB_Reserved,
t.database_transaction_log_bytes_used_system / 1024.0 AS LogKB_Used_System
FROM sys.dm_tran_database_transactions t
JOIN sys.dm_exec_sessions s ON t.transaction_id = s.open_transaction_count
JOIN sys.databases d ON t.database_id = d.database_id
WHERE s.session_id = 545;
```
???? **LogKB_Used** ??? Log space already used by the transaction (KB)
???? **LogKB_Reserved** ??? Reserved log space for the transaction (KB)
???? **LogKB_Used_System** ??? Log space used by system operations related to the transaction
---
### **2?????? Identify Tables Affected by the Transaction**
You can determine the **tables involved** in the transaction by checking the **locks held**:
```sql
SELECT
tl.resource_type,
tl.resource_description,
tl.request_mode,
tl.request_status,
t.&#91;name] AS table_name,
s.&#91;text] AS sql_text
FROM sys.dm_tran_locks tl
LEFT JOIN sys.objects t ON tl.resource_associated_entity_id = t.object_id
LEFT JOIN sys.dm_exec_requests r ON tl.request_session_id = r.session_id
OUTER APPLY sys.dm_exec_sql_text(r.sql_handle) s
WHERE tl.request_session_id = 545;
```
???? **request_mode** ??? Lock type (e.g., `X` for exclusive, `S` for shared)
???? **resource_description** ??? Index or key being locked
???? **table_name** ??? Affected table
???? **sql_text** ??? The exact SQL running
---
### **3?????? Track Transaction Progress**
If the transaction is **bulk insert/update/delete**, estimate the remaining work:
```sql
SELECT
r.session_id,
r.percent_complete,
r.estimated_completion_time / 1000 AS est_seconds_remaining
FROM sys.dm_exec_requests r
WHERE r.session_id = 545;
```
---
### **4?????? Find Transaction Details in the Log (Advanced)**
You can query the transaction log using `fn_dblog`:
```sql
SELECT
&#91;Transaction ID],
&#91;Operation],
&#91;Context],
AllocUnitName,
&#91;Transaction Name],
&#91;RowLog Contents 0]
FROM fn_dblog(NULL, NULL)
WHERE &#91;Transaction ID] IN
(SELECT transaction_id FROM sys.dm_tran_session_transactions WHERE session_id = 545);
```
???? **Operation** ??? Type of change (INSERT, DELETE, UPDATE, LOP_BEGIN_XACT, LOP_COMMIT_XACT)
???? **AllocUnitName** ??? Table or index being modified
???? **RowLog Contents** ??? Data affected
---
### **???? Summary**
??? **To check log space usage:** `sys.dm_tran_database_transactions`
??? **To find affected tables:** `sys.dm_tran_locks`
??? **To estimate completion time:** `sys.dm_exec_requests`
??? **To inspect log entries:** `fn_dblog`
Would you like help analyzing **log growth impact** or **rollback risk**? ????
Author: user
the first query, without a where statement, when i know i have an open transaction, is returning zero rows:
SELECT
s.session_id,
t.transaction_id,
t.database_id,
d.name AS database_name,
t.database_transaction_log_bytes_used / 1024.0 AS LogKB_Used,
t.database_transaction_log_bytes_reserved / 1024.0 AS LogKB_Reserved,
t.database_transaction_log_bytes_used_system / 1024.0 AS LogKB_Used_System
FROM sys.dm_tran_database_transactions t
JOIN sys.dm_exec_sessions s ON t.transaction_id = s.open_transaction_count
JOIN sys.databases d ON t.database_id = d.database_id
Author: ChatGPT
It looks like the **join condition** between `sys.dm_tran_database_transactions` (`t`) and `sys.dm_exec_sessions` (`s`) is incorrect. The column `open_transaction_count` in `sys.dm_exec_sessions` does not represent a transaction ID???it only counts open transactions for the session. That???s why the query is returning **zero rows**.
---
### ??? **Correct Query to Get Log Usage for an Active Transaction**
Use **`sys.dm_tran_session_transactions`** to correctly join with `sys.dm_tran_database_transactions`:
```sql
SELECT
st.session_id,
tdt.transaction_id,
tdt.database_id,
d.name AS database_name,
tdt.database_transaction_log_bytes_used / 1024.0 AS LogKB_Used,
tdt.database_transaction_log_bytes_reserved / 1024.0 AS LogKB_Reserved,
tdt.database_transaction_log_bytes_used_system / 1024.0 AS LogKB_Used_System
FROM sys.dm_tran_database_transactions tdt
JOIN sys.dm_tran_session_transactions st ON tdt.transaction_id = st.transaction_id
JOIN sys.databases d ON tdt.database_id = d.database_id
WHERE st.session_id = 545;
```
---
### **???? Explanation of Fix**
- `sys.dm_tran_session_transactions` **links transactions to sessions**, which was missing in the original query.
- The incorrect join on `s.open_transaction_count = t.transaction_id` was replaced with `st.transaction_id = tdt.transaction_id`.
- Now it correctly pulls **log space usage** for transactions tied to your session.
---
### **???? Troubleshooting If No Rows Return**
1. **Confirm the session still exists**
```sql
SELECT * FROM sys.dm_exec_sessions WHERE session_id = 545;
```
- If it returns no rows, the session has already ended.
2. **Check if there are active transactions**
```sql
DBCC OPENTRAN;
```
- If there are no active transactions, then `sys.dm_tran_database_transactions` won???t return results.
3. **See if any other transactions exist**
```sql
SELECT * FROM sys.dm_tran_database_transactions;
```
- If this returns no rows, there may be **no active transactions in the system**.
---
### ???? **Next Steps**
- If you confirm the transaction is still running but this query returns **zero rows**, let me know and we can dig deeper into `fn_dblog()`. ????
Author: user
in sql server, can i start a multi step job on a specific step, and not allow it to go to teh subsequent steps? EXEC msdb.dbo.sp_start_job N'job_name' , 'step_name'
Author: ChatGPT
In SQL Server, you **cannot** directly start a job from a specific step using `sp_start_job` alone. However, you **can** work around this by modifying the job execution behavior.
---
### ??? **Option 1: Use `sp_start_job` With a Specific Step**
You can specify the step to start **using the undocumented** `@step_name` or `@step_id` parameter:
```sql
EXEC msdb.dbo.sp_start_job
@job_name = N'job_name',
@step_name = N'step_name';
```
or
```sql
EXEC msdb.dbo.sp_start_job
@job_name = N'job_name',
@step_id = 3; -- Replace 3 with the step number
```
???? **Caveat:** This starts the job at the specified step, but **it will continue to the next steps unless explicitly configured otherwise**.
---
### ??? **Option 2: Modify the Job Step Logic**
To **prevent** the job from moving to subsequent steps:
1. **Open SQL Server Agent ??? Jobs ??? Select the Job**
2. **Right-click ??? Properties ??? Steps**
3. **Select the Step You Want to Start**
4. In the "Advanced" tab, set **"On Success Action"** to `Quit the Job Reporting Success`.
5. Set **"On Failure Action"** to `Quit the Job Reporting Failure` (optional).
---
### ??? **Option 3: Manually Run a Specific Step Using T-SQL**
Instead of starting the SQL Agent job, you can manually execute the command inside a specific step using:
```sql
USE &#91;DatabaseName];
EXEC dbo.MyProcedure; -- Replace with the step???s command
```
???? This ensures **only the selected step runs** and does not continue to the next steps.
---
### ???? **Best Approach?**
If you want to start from a **specific step** and ensure it **does not move to the next**, the best method is **Option 2 (modify the job step to quit on success)**.
Would you like a script to modify an existing job???s step behavior dynamically? ????
Author: user
for teh transactions log growth by spid, woudl the transaction growth itself be larger than the space we calcualtede? for example, my log has grown by 100GB, but the value in the query returns just 9kb
Author: ChatGPT
Yes, it is possible for the actual **transaction log growth** to be much larger than the value reported by the query from `sys.dm_tran_database_transactions`. Here???s why:
---
### ???? **Reasons Why Log Growth Exceeds Reported Transaction Log Space**
1. **Log Space Queries Only Show the Current Usage, Not Total Impact**
- The `database_transaction_log_bytes_used` column in `sys.dm_tran_database_transactions` reports the **currently allocated** log space **for active transactions**, not the total space the transaction has consumed over time.
- If the transaction has **committed parts of its work**, the reported usage may be much smaller than the log file???s total growth.
2. **Virtual Log Files (VLFs) and Autogrowth**
- When the log file grows, SQL Server does **not** shrink it automatically.
- If a transaction causes multiple autogrowth events, the log file may be **100GB larger**, but only **a fraction is currently occupied** by the transaction.
3. **Log Space is Reused or Reclaimed**
- `sys.dm_tran_database_transactions` only shows log records that are **currently active**.
- If the transaction was long-running and **logged a lot of changes that were later overwritten or cleared**, the reported usage can appear smaller.
4. **Log Buffering and Checkpoint Behavior**
- Some log records are **flushed to disk** only when necessary (lazy writes, indirect checkpoints).
- The transaction might have **forced excessive logging** (e.g., large updates, minimal logging disabled), causing log growth beyond what is visible in the DMV.
5. **Implicit or Explicit Transaction Management**
- If multiple transactions ran under **one SPID**, the log may have grown due to **previous transactions that are now committed**, but the query only reports the **current uncommitted transaction**.
---
### ??? **How to Get a More Accurate Log Space Usage Report**
#### **1?????? Check Total Log Space Used**
To see how much log space is actually used in the file:
```sql
DBCC SQLPERF(LOGSPACE);
```
This gives you:
- `Log Size (MB)`: Total allocated log file size.
- `Log Space Used (%)`: How much of it is currently in use.
---
#### **2?????? Check the Largest Transaction in the Log**
To find **which transaction used the most log space**:
```sql
SELECT
transaction_id,
database_id,
database_transaction_log_bytes_used / 1024.0 AS LogKB_Used,
database_transaction_log_bytes_reserved / 1024.0 AS LogKB_Reserved
FROM sys.dm_tran_database_transactions
ORDER BY database_transaction_log_bytes_used DESC;
```
This helps you see if another transaction caused the log growth.
---
#### **3?????? Check the Log File Growth History**
To see **how often and how much the log file has grown**:
```sql
SELECT
name AS database_name,
growth / 128.0 AS growth_MB,
&#91;size] / 128.0 AS total_size_MB,
is_percent_growth
FROM sys.master_files
WHERE type_desc = 'LOG';
```
This shows if **multiple autogrowth events** occurred.
---
#### **4?????? Find Active Transactions Holding Log Space**
To see if a transaction is **preventing log reuse**, run:
```sql
SELECT
log_reuse_wait_desc
FROM sys.databases
WHERE name = 'YourDatabaseName';
```
If the result is:
- **ACTIVE_TRANSACTION** ??? A long-running transaction is keeping log space.
- **LOG_BACKUP** ??? The log file cannot shrink until a backup is taken.
---
### ???? **Key Takeaways**
- `sys.dm_tran_database_transactions` **only reports active transaction log usage**, which is **often much smaller** than total log file growth.
- SQL Server **does not shrink the log file automatically**, even after a transaction commits.
- Log **autogrowth events**, **log reuse policies**, and **buffering behavior** can cause discrepancies between **log growth** and **reported transaction usage**.
Would you like help finding **which query caused the log to grow so much**? ????