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, in order to ensure transaction persistence even if the transaction fails. This is generally referred to as no-datablock-force-at-commit. 3.4 thread checkpoint event When a thread checkpoint event occurs, the dirty data protected by the redo record whose SCN is less than the specified value will be refreshed to the data file. After completion, the thread checkpoint
, commit forces the log to refresh to the disk-at least until the redo record of commit, which is generally called log-force-at-commit. Recovery is designed to be like this. When the transaction commit, you only need to refresh the redo record to the redo log, instead of refreshing all the dirty data modified by the transaction, in order to ensure transaction persistence even if the transaction fails. This is generally referred to as no-datablock-force-at-commit. 3.4 thread
[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
, it is necessary to do etrollover operationsGgsci>alter Extract ExttretrolloverGgsci>alter Extract Dpetretrollover3.5 Modifying the source-side DataPump process extseqno and Extrba numbersBecause the extract-exttr process on the source side performs the etrollover operation, the Extseqno and Extrba of the process are reset to the No. 0 extseqno of the next Extrba number, And DataPump did not know that the extract process took place this change, still watch in extract etrollover before the extse
MySQL series: innodb source code analysis-redo log structure, mysqlinnodb In innodb Engine implementation, a redo log system is built to ensure transaction persistence. Redo log is composed of two parts: the memory log buffer and the redo log file. The purpose of this design is obvious. The log buffer is to speed up log writing, and redo log files to provide persistence for log data. In the innodb redo log system, the following concepts are introduced in order to better achieve log recoverabilit
parameter Db-block-write-batch.When a server process looks for the db-block-max-scan-cnt buffer in the LRU table, it does not find the unused buffer, it stops finding and notifies DBWR to write. A timeout (3 seconds per time) occurs and DBWR notifies itself. When a checkpoint occurs, LGWR notifies DBWR. In the first two cases, DBWR writes the block in the dirty table to disk, each time the number of writable blocks is specified by the initialization
-inclusive characteristic also has its shortcoming, often the performance and the stability cannot keep up with, seemingly cannot satisfy the telecommunication class enterprise. For small and medium-sized enterprises that are interested in enhancing their perimeter security services, UTM equipment is very cost-effective. For the selection of UTM products, reference to the 2011 Best Unified Threat Management (UTM) products. Often used to compare with UTM when the next generation of firewalls (
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
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
written and guaranteed to be rolled back, making it possible to roll back all modifications if the commit fails. The redo information here is actually the redo information of the rollback segment. Write-priority protocols guarantee the atomicity of transactions in the database transaction layer. 3.3 Transaction Submission When a transaction commits, a SCN is assigned and a redo log record containing that SCN submission is established. The commit process does not end when some redo records (i
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
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
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
1. Example of a calculator (manually add and write the result to the log file) systemutil. run "C: \ windows \ system32 \ calc.exe", "", "C: \ WINDOWS \ System32", "open" window ("Calculator "). winbutton ("1 "). click window ("Calculator "). winbutton ("+ "). click window ("Calculator "). winbutton ("2 "). click window ("Calculator "). winbutton ("= "). click 'Insert --> output value --> standard output value -->... window ("Calculator "). winedit ("edit "). output
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