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Each database of Sybase SQL Server, whether it is a system database master, model, sybsystemprocs, tempdb) or a user database, has its own transaction log, and each database has a syslogs table. Logs record user operations on the database, so if you do not need to clear the Log, the log will continue to grow until the occupied space. You can run the dump transaction command to clear logs, or use the trunc log on chkpt option to clear logs automatically at intervals. Managing database logs is a m
The incremental checkpoint is used to balance the load. It is triggered by the fast_start_mttr_target parameter and is incrementally written out. Therefore, CHECKPOINT_CHANGE # is delayed and will not be updated immediately.Three methods are used to prove the problem:Method 1:Theory: logs are active, that is, logs overwritten by RBA pointers. If the checkpoint is complete, RBA will immediately redo the last
database consistency state at the beginning of the dump. 2. Load a copy of the log file closest to the time of the failure, and restore the database to the consistent state when the log file was dumped, using the method of recovering the system failure. 3. Rerun the transaction from the most recent dump log file to any modified data at the time of the failure. To restore the database to a consistent state at the point of failure). Database recovery technology with
When talking about the transaction log, we have to talk about the checkpoint Checkpoint, referred to as CKP. Both transaction logs and checkpoints exist for the rapid recovery of the database. We need to know what the checkpoint is and what it has to do with the transaction log. What's CKP for? It is well known that the data changes are not written directly int
to be written out to gain a performance boost for batch effects. Similar to Redo log buffer, the Redo log file is also used for recycling, and Oracle allows a minimum of two log groups. By default, 3 log groups are established when the database is created. Sql> select Group#,members,status from V$log;group# Members STATUS---------- ---------- ----------------1 1 INACTIVE2 1 Current3 1 INACTIVE When a log file is full, it switches to another log file, which is called log switch. Log switch trigg
also accelerate the recovery process, less processing a log. Therefore, the disk write time of the log buffer can be postponed, late than the transaction commit. In fact, there are some other restrictions on the implementation of the log buffer, such as checkpoint, the log buffer is full, and not necessarily wait until the transaction commits to write to the disk.4. The origin and function of LSNNow that you have the log, you have to play its role in
V $ database. CONTROLFILE_CHANGE # (indicates the last scn Number of the control file recovered from the backup. If the control file is not V $ database. CONTROLFILE_CHANGE # (indicates the last scn Number of the control file recovered from the backup. If the control file is not V $ database. CHECKPOINT_CHANGE # (last scn checkpointed)V $ database. CONTROLFILE_SEQUENCE # (control file sequence number incremented by control file transactions)V $ database. CONTROLFILE_CHANGE # (last scn in back
entries. This delay improves data writing performance, such as batch effects. Similar to Redo Log Buffer, Redo Log File is also used cyclically. Oracle allows at least two Log groups. By default, three log groups are created during database creation. Sys @ NEI> select group #, members, status from v $ log; GROUP # members status ------------ ------------------ 1 1 INACTIVE 2 1 CURRENT 3 1 INACTIVE when a log file is full, switch to another Log file, which is called Log Switch. Log Switch trigge
data in batches.Similar to redo log buffer, redo log file is also used cyclically. Oracle allows at least two log groups. By default, three log groups are created during database creation.SQL> select group #, members, status from V $ log; Group # members status------------------------------------1 1 inactive2 1 Current3 1 inactiveWhen a log file is fully written, it is switched to another log file, which is called a log switch. Log switch triggers a checkpo
V $ database. CHECKPOINT_CHANGE # (last scn checkpointed)V $ database. CONTROLFILE_SEQUENCE # (control file sequence number incremented by control file transactions)V $ database. CONTROLFILE_CHANGE # (last scn in backup control file; null if the control file is not a backup)V $ datafile. CHECKPOINT_CHANGE # (scn at last checkpoint)V $ datafile_header. CHECKPOINT_CHANGE # (datafile checkpoint change #V $ log
SCN is the internal clock of Oracle, which is used to reflect changes in the database and is constantly updated during operation. SCN types include: SCN is the internal clock of Oracle, which is used to reflect changes in the database and is constantly updated during operation. SCN types include: SCN is the internal clock of Oracle, which is used to reflect changes in the database and is constantly updated during operation. SCN types include: (1) Current SCN OF THE SYSTEM (2)
A checkpoint is actually a record of past history and can be considered as a log. however, this is simplified. for example, I have another piece of text. there are a pile of links in the text. my current task is to download the content from those addresses. in addition, due to network problems or website problems, each download may not be very successful. A chain disconnection or socket Exception error may occur. However, no matter what kind of errors
multiple online redo logs and place them on separate disks, and it is recommended that you store multiple backups on the same disk, even if you cannot put them on multiple disks, to avoid I/O failure. The multiplexing of online redo logs can affect performance, but the priority of the database is reliability. 650) this.width=650; "src=" http://s3.51cto.com/wyfs02/M00/4A/5E/wKioL1QkeFrBjY5TAAGfKL36Qqc284.jpg "title=" 6.png " alt= "Wkiol1qkefrbjy5taagfkl36qqc284.jpg"/>Members of a group should be
When Will instance recovery be generated after in-depth analysis of instance recovery? When your database server suffers an abnormal power failure, instance recovery will occur when you restart the database. Instance recovery is automatically completed by the database without DBA interference. Of course, there is a premise: data files, online log files, and control files must not be damaged. Let's use an experiment to analyze the whole process of instance recovery! 1. Before shutting down the da
background processes if necessary.· Register an Oracle instance with the Oracle TNS Listener 2.SMON: System Monitor(System Monitor)· Clear temporary space· Merge free spaceIf you are using a dictionary-managed tablespace, SMON is responsible for obtaining consecutive idle segments in the tablespace and merging them into a larger idle segment.· Recover the transaction for the original unavailable files: This is similar to the role of SMON when the database is started· Restore instances of failed
The principle of instance recovery when the database suddenly crashes, it is not time to refresh the dirty data blocks in the buffer cache to the data file, at the same time, when a transaction is suddenly interrupted when the instance crashes, the transaction is in the intermediate state, that is, neither commit nor rollback. At this time, the content in the data file cannot reflect the status of the instance crash. In this way, the closed database is inconsistent. The next time you start an in
Oracle architecture learning notes: the most important thing for oracledatabase is onlineredolog, ldquo; write rdquo;: Checkpoint Process computing workload to set checkpoints, Oracle architecture learning notes, the most important of oracle database is online redo log, ldquo; write rdquo;: Checkpoint Process computing workload, to determine the checkpoint,
not become the bottleneck of HDFS operations, hadoop adopts the following method: No snapshot of the current file system is persisted, the list of HDFS operations in the recent period will be saved to an editlog file in namenode. When the namenode is restarted, in addition to the load fsimage accident, the HDFS operation recorded in the editlog file will be replaced to restore the final state before the HDFS restart. Secondarynamenode periodically merges the HDFS operations recorded in the edi
1. Meta Data Management OverviewHDFs metadata, grouped by type, consists mainly of the following sections:1, the file, the directory of its own property information, such as file name, directory name, modify information and so on.2. Storing information about the information stored in the file, such as block information, block case, number of copies, etc.3, records the Datanode of HDFs information, for Datanode management.In the form of memory metadata and metadata files two, respectively, there
I. When do I need instance recovery? In shutdown normal or shutdown immediate, the so-called clean shutdown will automatically trigger the checkpoint and write the SCN record back. When a checkpoint occurs, the SCN is written to four places: Three places are in the control file: (1) SYSTEM CHECKPOINT SCN (2) Datafile checkpoi
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