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Questions tagged [checkpoint]

checkpoint is a database event. when checkpoint happens, all dirty blocks(pages) in the memory are written to database data files.

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Behavior of PostgreSQL checkpoint_timeout when the previous checkpoint is still in progress

Dear PostgreSQL Community, I am trying to better understand PostgreSQL checkpoints internally, so I was thinking about this scenario. Lets say we have checkpoint_timeout 15 mins and ...
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How to flush WAL files?

I'm trying to force WAL files to be flushed on to the disk so that I can copy them somewhere else. I believe CHECKPOINT is the command I'm interested in but it doesn't seem to work. I have a docker ...
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SQL Server 2014 Negative log. Stuck at CHECKPOINT. Unable to do anything

I have a database that is stuck at CHECKPOINT for hours and I already tried all solutions that have been suggested in this site with no avail and I'm starting to lose faith. Keep in mind that the ...
Pedro's user avatar
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Shared buffers, WAL buffers and Checkpointers

I am taking this EDB PostgreSQL essential course and Instructor explained about PostgreSQL architecture referring to the diagram that, whenever a client make an update request and suppose data is ...
commonSense's user avatar
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Clarification on Automatic Checkpoints and IO Latency Thresholds in SQL Server

I have been reading the SQL Server documentation and came across the following statement about automatic checkpoints: Issued automatically in the background to meet the upper time limit suggested by ...
Fajela Tajkiya's user avatar
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Postgres 14 WAL FILE cannot change min wal size(in WAL DIRECTORY) after changing propperties min_wal_size max_wal_size

I'm completely new in Postgres optimization. I was reading a lot about checkpoint and WAL files. I found a query to examine the ratio of checkpoints time to requested (exceeded WAL max size) SELECT ...
BARTOSZ BALA's user avatar
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What is the purpose of indirect checkpoint when the default checkpoint time (when recovery time is 0) does a 1 minute checkpoint?

Indirect checkpoint is performed when the target recovery time is configured. When the value is 0, then it will do checkpoints such that default recovery time is 1 minute. Where as if the value is ...
variable's user avatar
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What is difference between checkpoint_timeout and checkpoint_completion_target in PostgreSQL?

I am MSSQL guy and I find it a bit difficult to understand the main purpose of checkpoint_completion_target. I cannot find a comprehensive resource that would explain more clearly the difference ...
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Recovery of uncommitted transactions after checkpoint

After reading from several resources including: COMMIT (Oracle Database SQL Reference) Checkpoints (Oracle Programmer Reference) Difference between commit and checkpoint (on this site) ORACLE ...
shantanu4raje's user avatar
3 votes
2 answers
502 views

In SQL Server, what's the impact of a checkpoint to log records in log buffer?

Does checkpoint operations flush everything in the log buffer to log file? Or just the log records relating to the dirty pages that are about to be flushed? I found some inconsistent description about ...
Just a learner's user avatar
5 votes
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Dirty buffer pages after issuing CHECKPOINT

I am currently working on a test system and due to the nature of the queries I want to optimise, I am trying to simulate a "cold" read a well as I can. Part of that is clearing the buffer ...
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Why xlog checkpoint was started?

Consider the following config shared_buffers = 20GB max_wal_size = 2GB min_wal_size = 1GB checkpoint_completion_target = 0.7 checkpoint_timeout = 5min and checkpoints' log 2020-05-25 16:28:37.128 ...
sim's user avatar
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Why does SQL Server start REDO phase from minLSN instead of last CHECKPOINT?

while reading an article from BOL, I stuck on the picture which explains the recovery process of database (without ADR): Shouldn't Phase 2:Redo start from Last CHECKPOINT as till that point ...
Rauf Asadov's user avatar
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TempDB Transaction log not releasing space

Every time I complete a transaction in tempdb, the temp log grows, however the log doesn't seem to release the space once the transaction has completed.The log usage percent is 43.4% but seems to ...
Krishnp92's user avatar
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Checkpoints on secondary replica AlwaysOn AG

Setup 3 Node Alwayson cluster - 1 sync and 1 async secondary replica - SQL Server 2012 Situation We are witnessing PageIOLatches when reading from the asynchronous secondary replica. This is ...
Thomas Costers's user avatar
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1 answer
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System failure causes inconsistency between two transactions

Let's say the picture above the transaction 4 for user A. A updated a record from Account table, change the balance from 100 to 0, then a checkpoint occurred, so all dirty pages got written to disk. ...
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How SQL Server transaction works with log records

My textbook says: Starting when you begin a transaction, your changes are isolated from other users. What you’re doing is visible to you only,and isn’t really done until you COMMIT — although it ...
secondimage's user avatar
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WAL buffer checkpoint/flush time during serialization isolation

I have a doubt regarding the flush/checkpoint time of WAL buffers during serialization isolation in Postgres. Is it possible to lose acknowledged writes even if transaction runs in serialization ...
Dikshant Rathi's user avatar
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When should CHECKPOINT be added to stored procedures

I would like to know when is the proper moment to append a manual CHECKPOINT in a stored procedures (or function)? I didn't see anything different apparently after applying the CHECKPOINT to some of ...
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High number of Checkpoint pages/sec and memory pressure

Recently I read a blog post on mssqltips.com about memory bottlenecks on SQL Server. In this article I read following: The following performance counters on SQL Server: Buffer Manager object can ...
Frederik Vanderhaegen's user avatar
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Keep a history of transactions for easy rollback

Is there a database (either SQL or NoSQL) which allows you to keep a history or log of all past transactions so that you can easily rollback to any given point in time (similar to how git manages a ...
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In Full recovery mode, when does the buffer/transaction log changes get applied to the database data pages?

When a change is to be made, the data page is fetched from the database data file into the buffer and changes are made to the buffer page and are also written to the transaction log. Write ahead ...
variable's user avatar
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9 votes
1 answer
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What Happens to dirty pages if the system fails before the next checkpoint?

Assuming a database using full recovery model, when a record is written in SQL Server (by INSERT / UPDATE etc) write ahead logging will ensure the change is written to the log file before modifying ...
SE1986's user avatar
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10 votes
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Increased waits during checkpoint after upgrading to better storage

When we migrated from an older all flash array, to a newer all flash array (different, but well established vendor), we started seeing increased waits in SQL Sentry during checkpoints. Version: ...
Doley's user avatar
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Postgresql sometimes gets high IO issue

I have a Sanic app using asyncpg (0.13) to work with postgresql (9.5). My server now facing a problem which sometimes postgresql seems to be freezed and my app can't even read from db and it seems ...
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2 answers
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PostgreSQL checkpoint log explained

I know what PostgreSQL checkpoint is and when it is happening. I need some additional information about the logs produced by the log_checkpoints = on parameter, so please explain some points of it to ...
inivanoff1's user avatar
3 votes
1 answer
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MongoDB responds slowly during the WiredTiger Checkpoint writing process

We have 3 instances of MongoDB 3.2.12 configured as a replica set. Journaling is enabled, the storage engine is WiredTiger. Most of the time our application produces a very low load on the database ...
RomanG's user avatar
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SQL Server: can I restore full DB file backup to First LSN (i.e. when backup started)? [duplicate]

A full database backup was started at 15:46:00 using the following cmd: backup database IF_BROWNS to disk = 'C:\temp\IF_STDINT_{0}.BAK' (where {0} = timestamp, e.g. 2017-05-16T15-46-00.0831634+01-00) ...
Laurence's user avatar
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2 answers
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Does not writing a checkpoint record damage anything?

I got an alert Event ID: 3619. Could not write a checkpoint record in database 'ID ####' because the log is out of space I know why it happened, I have addressed the issue, backed up the t-logs, ...
James Jenkins's user avatar
5 votes
2 answers
1k views

Using CHECKPOINT vs GO

Typically, when one of the developers or data analysts needs to perform a very large update or deletion of data (where a truncate or truncate/insert wouldn't make sense because the data set to keep is ...
Alf47's user avatar
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What does "Deleting unrecoverable checkpoint table row" mean?

When I look at our production SQL Server 2016's server logs I am seeing multiple entries that say: [INFO] Database ID: [5]. Deleting unrecoverable checkpoint table row (id: 294). The id at the ...
Brian P. Hamachek's user avatar
2 votes
0 answers
770 views

Amount by which to increase checkpoint_segments (postgresql)

In my postgresql log, I see statements such as checkpoints are occurring too frequently (26 seconds apart). Currently in the conf, checkpoint_segments are 32, checkpoint_timeout is 15 mins and ...
Hassan Baig's user avatar
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2 votes
1 answer
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How does Checkpoint know which point to recover from in PostgreSQL?

I'm trying to better understand Checkpoint internals, specifically in PostgreSQL. My current understanding is that Crash Recovery will always start from the latest REDO location that is marked when a ...
Dave Stibrany's user avatar
1 vote
2 answers
239 views

Checkpoint during Backup

Can database process make automatic checkpoint when I'm in process of copying files during ALTER DATABASE BEGIN BACKUP; and ALTER DATABASE END BACKUP; You can assume that process of copying ...
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19 votes
1 answer
39k views

Checkpoints are occurring too frequently during pg_restore

Under PostgreSQL 9.2.2 (Windows 32 bits), I have a pg_restore command that systematically results in log warnings about the checkpoint frequency, for example: LOG: checkpoints are occurring too ...
Sébastien Clément's user avatar
11 votes
1 answer
12k views

"truncate log on checkpoint" option in SQL Server

Long story but our long term consultants (former employees) wrote a custom script years back (2006 or so) to interface with Tivoli Storage Manager and it appears to be checking for a SQL Server DB ...
user3885315's user avatar
2 votes
1 answer
208 views

Postgres 9.1.16 Hot Standby

I am using PostgreSQL 9.1.16 (and I cannot upgrade) with Hot Standby. We have a few batches that perform some heavy writes, resulting in a lot of WAL bein produced in a short period of time. The ...
Mael's user avatar
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3 votes
1 answer
325 views

Checkpoints and Logging

I'm working on getting full grasp of logging architecture. Please correct me if I'm wrong here: I understand that a checkpoint occurs (also lazywriter) to write the dirty pages in the memory to the ...
Stackoverflowuser's user avatar
6 votes
1 answer
39k views

How can I solve postgresql problem after deleting wal files?

I turned the archive_mode on on my postgresql configuration for testing a backup server . And since the wal files took lots of disk space, after my test I turned it off and also deleted the wal files. ...
Sina's user avatar
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1 vote
2 answers
999 views

Are logs in the LDF file being removed after a checkpoint?

Using the fn_dblog I can get the active portion of the online transaction log of my database. But after every checkpoint I can only see 2 entries showing the beginning of the checkpoint ...
Amer Sawan's user avatar
2 votes
0 answers
347 views

What is an incremental checkpoint (in the context of indirect checkpoints)?

I was using extended events to trace checkpoint activity of a database with indirect checkpoints enabled. The event stream looks like this: And the details of the selected event are: The description ...
usr's user avatar
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1 vote
1 answer
2k views

Sql Server rollback to some point in time

This seems like a fairly common scenario, yet I'm not sure how to do this. I have a very large database (think a lot of terabytes), which makes it impossible to create a full backup. At some point, I ...
user avatar
6 votes
2 answers
15k views

MS SQL Server - Checkpoint process stuck in SLEEP_BPOOL_FLUSH

We seem to have a problem that came out of nowhere. The checkpoint process is stuck in SLEEP_BPOOL_FLUSH state, and not actually reducing the usage in the log file. This never seemed to happen before....
apt605's user avatar
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3 votes
1 answer
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What happens when checkpoint_segments reached?

I'm a bit confused with checkpoint_segments definition in PostgreSQL documentation. What happens when checkpoint_segments reached? The dirty pages in shared_buffers written to WAL. Then what is the ...
Majid Azimi's user avatar
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3 votes
3 answers
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What does "thread" mean in "thread checkpoints" context?

The following excerpt is from Oracle concepts. Maybe this is a stupid question, but I really need your help to understand it. My question is: What's does the thread mean in the context thread ...
Just a learner's user avatar