checkpoint 13500

Data | database Working diagram of a transaction Transactions ensure the consistency and recoverability of data. The transaction works as shown in Figure 1. Figure 1 Working schematic diagram of a transaction After the transaction starts, all the operations of the Office are written to the transaction log in succession. There are generally two types of operations written to the log: one for data manipulation and one for task operations. Operations on data, such as insertions, deletions

write IO线程数（innodb 1.0x） purge thread ： 事务提交后，其所使用的undolog就不再需要，所以需要存储引擎负责回收并分配新undo页； innodb1.1x之前 purge动作在master thread中完成； 之后可以通过配置 innodb_purge_threads=1 开启独立的purge thread来处理，以减轻master thread负担，提高CPU使用率； page cleaner thread : innodb1.2x版本开始，将脏页刷新操作放在单独的page cleaner thread中，进一步减轻了master thread负担，并减轻用户查询线程的阻塞；Buffer pool缓冲池： 缓冲池本质上就是一块内存区域，通过内存的速度弥补磁盘速度较慢对数据库性能的影响； 在数据库中进行读取操作时，首先判断待读取页是否存在缓冲池中； 如果存在，则缓冲池命中，直接从缓冲池中读取进行后续操作； 否则进行io操作，从磁盘中读取页，然后存

it is monitoring the database, it is rarely necessary for an administrator to recover from an instance failure. When a DB instance fails, Oracle Restart attempts to restart the instance. If manual intervention is required, there may be a more serious problem preventing the instance from restarting, such as a memory CPU failure. Understanding Instance Recovery: Checkpoint (CKPT) session To understand instance recovery, you need to unders

Oracle Learning--buffer Cache in-depth analysis650) this.width=650; "src=" http://s3.51cto.com/wyfs02/M02/40/BE/wKioL1PPVxOwPpjTAAL_LJN_ltc591.jpg "title=" 1.png " alt= "Wkiol1ppvxowppjtaal_ljn_ltc591.jpg"/>Server process and database buffer cache:When a block is required by the server, the block needs to be read by series steps:1. First, the server uses a hash function to check whether the required blocks can be obtained from the buffer cache. If a buffer is found, it is moved to the LRU list

sequence number when a dirty page is modified, and also to record checkpoint, which, through the LSN, can be specifically located in the Redo log file.To manage the dirty pages, the page on each instance in Buffer Pool is maintained on a flush List,flush list, sorted by the LSN number in which the page was modified. So when doing redo checkpoint periodically, the LSN of choice is always the oldest page on

acting on the buffer, and then dbwn will dump the dirty buffers into the disk. 　　When does Dbwn write? Dbwn is a lazy process that writes as little as possible , in the following four cases it performs writes: A. There is no buffer available (you have to write it) B. Too many dirty buffers C.3 seconds Timeout (writes are performed once at the latest 3 seconds) D. A checkpoint, checkpoint (

, password Tiger successfully logged into database. Ggsci (localhost.localdomain) 2> add trandata scott.tcustmer Logging of supplemental Redo data enabled for table SC OTT. Tcustmer. Ggsci (localhost.localdomain) 3> add trandata scott.tcustord Logging of supplemental Redo data enabled for table SC OTT. Tcustord.First, the initialization of loading dataConfigure an initialization extract on the source side to synchronize existing data in the tableGgsci (localhost.localdomain) 7> ADD EXTRACT e

prior to the dbwn process and performs real-time write operations at the same time of submission, there is always enough information in the redo stream, this allows you to rebuild any submitted changes that have not been written to the data file and roll back any uncommitted changes that have been written to the data file. The instance recovery mechanism of redo and rollback makes it impossible for the Oracle database to have a Rolling Error. 3.3 adjust instance recovery MTTR (the average recov

Oracle SCN-system change number learning notes 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) Checkpoint SCN (note that it will only be updated with the occurrence of the checkpoint: But in hot standby mode, the SCN will not change during

that affects all the operators in the application, so the performance cost is also relatively large. If we know probably where the problem is, and the entire application to open debug mode, but also easy to be overwhelmed by the vast number of debugging information. At this point, we need a more precise and inexpensive way to locate.2.7.2 using Checkpoint () to locateIf you know which chain the problem is on, but because the chain is upstream or down

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 action is complete, Ora

. When a checkpoint occurs:Dbwr moves all dirty buffers from the LRU list to the dirty list and writes data.5. When tablespace starts Hot Backup:Dbwr moves all dirty buffers belonging to the tablespace from the LRU list to the dirty list and starts to write data.6. When tablespace is offline:Dbwr moves all dirty buffers belonging to the tablespace from the LRU list to the dirty list and starts to write data.7. When you execute drop:DropTableOrIndexThi

the root operation, so the reserved space can be used up, but it can still be deleted. "The problem" is whether the available disk space is zero after deletion. This is not a real problem, but it only requires nilfs-clean-p 1 s-r to tell nilfs-cleanerd not to keep the checkpoint one second ago, by default, it always retains checkpoints within one hour. NILFS snapshot is actually a specially marked checkpoint