[Msql] redo and undo log, msqlredoundolog
InnoDB has two very important logs: undo log and redo log. The former is used to ensure the atomicity of transactions and the MVCC of InnoDB, and the latter is used to ensure transaction persistence. Like most relational databases, InnoDB records physical changes to data files and ensures that logs are always logged first, that is, the so-called WAL (Write Ahead Log), that is, before a persistent data file, ensure that the previous redo logs have been wr
MySQL Engine Features-InnoDB redo log roamingPreface
InnoDB has two very important logs: undo log and redo log. The former is used to ensure the atomicity of transactions and the MVCC of InnoDB, and the latter is used to ensure transaction persistence.
Like most relational databases, InnoDB records physical changes to data files and ensures that logs are always logged first, that is, the so-called WAL, before the persistent data files, ensure that the previous redo logs have been written to the
scenario first emerged, followed by the ins and outs and needs of these problems, followed by the evolution of some design schemes, and finally some of them were standardized as models. Therefore, we will try to understand and analyze some examples of the design patterns we discuss in real life, and then try to summarize a design step by step, and finally summarize some designs that match some patterns. Design Patterns are discovered in these similar processes. What do you think?
Farhana: I th
DBWn: Database block writer (DatabaseBlockWriter) is responsible for the background process of writing dirty blocks to the disk. CKPT: CheckpointProcess
DBWn: the Database Block Writer is responsible for the background process of writing dirty blocks to the disk. CKPT: Checkpoint Process
DBWn: the Database Block Writer is responsible for the background process of writing dirty blocks to the disk.
CKPT: The Ch
large extent.
34 what is the difference between temporary tablespace and permanent tablespace?A: A temporary tablespace is used for temporary objects such as sorting structures and permanent tablespacesUsed to store the 'true' objects (such as tables and rollback segments)
35. What is the name of the tablespace automatically created when a database is created?Answer: System tablespace.
36. In Oracle databases, there are three types of checkpoints Based on the execution time.
First, the databa
DBWn: the Database Block Writer is responsible for the background process of writing dirty blocks to the disk.
CKPT: The Checkpoint Process is only the header of the file for updating the data file to assist in creating the Checkpoint Process (DBWn ).
LGWR: Log Writer is responsible for refresh and output the content in the SGA to the disk.
In fact, these three processes are designed to better accomplish on
file information.
Redo logs and archive logs.
Backup set and backup file information
Check Point and SCN information.
When the database is shut down normally, the SCN value in the control file
In the data file information section of the control file, each data file has a Checkpoint SCN and Stop SCN, which must be verified when the database is started.
We know how the database controls the SCN in the file when the consistency is disabled?
1. Close t
the reader to view the number of Wals that the continuous running database has committed the changes to at the same time. the transaction can also be appended to the end of a single Wal File
Operation
Of course, the append of a transaction to be finally transmitted to the wal file is copied back to the original database. Moving the wal file back to the database is called a "checkpoint"
Another method is that the difference between rollback and the Wi
EnablePart 3:auto discovery/enhanced Auto DiscoveryRiOS Auto-discovery ProcessStep 1:client send a SYN to the SteelHead.Step 2:steelhead Add a TCP option 0x4c to the SYN and it becomes syn+ than sent to the Server Side SteelHead. Also it sendStep 3:the Server Side SteelHead See the option 0x4c (*) also known as TCP probe. It respond an syn/ack+ back. This time the inner TCP Session has been establised.Step 4:the Server Side SteelHead sends a SYN to the server.Step 5:the Server respond the Syn/a
process writes dirty cache blocks to data files;
C. When a checkpoint LGWR process occurs, it notifies the DBWn process to perform write operations;
D. When a tablespace is in the backup mode, offline, or read-only state;
E. When the DBWn process times out (Time_out), that is, it is not started in about 3 seconds.
Ü role:
A. Manage High-Speed buffers to ensure that the server process can always find idle cache blocks to save data blocks read from dat
This articleArticleThis is the second article in the series, in case you have not read the first article. The address of the previous article is as follows:
Transaction logs in SQL Server (I)-physical and logical architecture of transaction logs
Introduction
Each SQL Server database records the corresponding logs to the log files according to the order of the modified data (insert, update, delete. SQL Server uses the write-Ahead Logging Technology to ensure the atomicity and durability of
a single extraction process4, the transmission process and the extraction process needs one by one correspondence;2.3. Splitting steps1. Stop Extract Process2. Stop DataPump ProcessGgsci> INFO Datapump_nameEXTRACTDPEF last Started 2011-01-28 12:34 Status RUNNINGCheckpoint Lag 00:00:00 (updated 00:00:05 ago)Log Read Checkpoint File./dirdat/ef0000102011-01-28 12:47:45.000000 RBA 148645Until the RBA number does not change, can stop3. Stop Replicat Proce
SBU IntroductionV1.0SBU ConceptSBU is a strategic business unit.The so-called "SBU" means "every employee is a company ". because there must be both a large enterprise scale and a rapid response from a small enterprise, the aircraft carriers of large enterprises must be transformed into countless independent combat subjects that can be split, rather than "independent from each other ", instead, we need to turn every employee into a "strategic institution", provide a "one-stop service" to the out
multiple VCenter Server instances in your environment.The installation of VCenter Server with external Platform Services Controller has the following disadvantages:VCenter Server and the Platform Services Controller establish connections over the network, which makes connection and name resolution problems easy.If you install VCenter server on a Windows virtual machine or physical server, you will need more Microsoft Windows licenses.You need to manage more virtual machines or physical servers.
When using Microsoft Exchange Server 2003, you must note the differences between recovery and recovery. Restoration refers to the restoration of databases and log files to the server. Restoration refers to the replay of transaction logs to the recovered database.
There are two forms of recovery:
Soft Recovery refers to the log replay process when the database is reloaded unexpectedly after it is stopped, or when the transaction log is replayed to the offline backup of the database.
The replay p
When using Microsoft Exchange Server 2003, you must note the differences between recovery and recovery. Restoration refers to the restoration of databases and log files to the server. Restoration refers to the replay of transaction logs to the recovered database.There are two forms of recovery:Soft Recovery refers to the log replay process when the database is reloaded unexpectedly after it is stopped, or when the transaction log is replayed to the offline backup of the database.The replay proce
In the implementation of InnoDB engine, the redo log system is built in order to realize the persistence of the transaction. The redo log consists of two parts: the Memory log buffer (redo log buffers) and the redo log file. The purpose of this design is obvious: The log buffers are designed to speed up the logging, and redo log files provide persistence for log data. In InnoDB's redo log system, the following concepts have been introduced in order to achieve better log recoverability, security,
About the SCN understanding
System Checkpoint SCN (V$database (checkpoint_change#))
Data file Checkpoint (V$datafile (checkpoint_change#))
Data file termination SCN (V$datafile (last_change#))
Checkpoints stored in data files
Start SCN (V$datafile_header (checkpoint_change#)
1. System Checkpoint SCN
When a checkpoint
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