Transaction A
Withdrawal Service B
T1
Start a transaction
T2
Start a transaction
T3
Inquiry account balance is 1000 yuan
T4
Remove 500 yuan balance modified to 500 yuan
T5
Inquiry account balance is 500 yuan (dirty Read)
T6
Undo transaction balance restored to 1000 yuan
T7
Import 100 yuan to change the balance to 600 yuan
T8
Commi
Brief introduction of Redis persistence:
Redis is a persistent memory database, which means that Redis often synchronizes data in memory to disk to ensure persistence. Redis supports two kinds of persistence, one is snapshotting (snapshot) is also the default, the other is Append-only file (abbreviated AOF) way. The following are described separatelySnapshottingSnapshots are the default persistence method. In this way, the memory data is written to the binary file as a snapshot, and the default
We should understand the role of float, is to eliminate the block element "hegemonism" a sharp weapon!
There are two ways of page layout1) Float float2) Positioning positionLet's have a little practice today to understand the meaning of float.ExampleRequirements:1) Two squares, a red #900, a blue #009;2 Red Square width and height are 200 pixels, blue squaresThe width is 300 pixels and the height is 200 pixels;3 The upper outer margin (margin-top) and
statement for top 15 that executes most frequently.SELECT sql_text, executions from (SELECT sql_text, executions, Over (ORDERbyDESC) Exec_rank from WHERE (a)I. SummaryWhen doing the consultation, check the operation of the previous SQL, and the conditions of the queryWhen querying bound variables, there are hard parsing and soft parsing points, and if it is soft parse, the value of the variable is difficult to findSeveral views
-policy VOLATILE-LRU: Use Lur algorithm to clean up old data when memory is fullDaemonize Yes: DaemonPidfile/va/run/redis_6379.pid: Process PIDPort 6379: Port numberTimeout 300: Link time-outLogLevel Notice: Log levelLogfile/var/log/redis_6379.log: Log fileDatabases 16: Number of databasesSave 900 1: Database Mirroring frequencyDbfilename Dump.rdb: Mirrored backup file name/va/lib/redis/6379: Backup file pathSave
CD-bash:alias:cd:not foundCD is an internal command belonging to the Bash software comes with commands (refer to man CD) it does not define aliases[Email protected] ~]#[[email protected] ~]# alias lsLS is defined as an aliasAlias ls= ' ls--color=tty '[Email protected] ~]#[[email protected] ~]# which LSAlias ls= ' ls--color=tty '/bin/ls[Email protected] ~]#LS is actually an external command that belongs to an executable program that is compiled from C code.[Email protected] ~]# File/bin/ls/bin/l
environment;Warning: Only important warning messages are displayed;LogFile stdout # #指定日志的输出路径, the default value stdout, indicating output to the screen, the Guardian mode is output to/dev/null;If you want to output the log to Syslog, you can start syslog-enabled Yes, which defaults to No.# syslog-enabled NoDatabases # # # #指定数据库的数量, default is 16, the default database used is DB 0.----The following snapshot-related settings:------# Save Save 900 1:
Model + Light Test results:Draw calls and memory used prior to executionDraw calls and memory used after execution? Model Consolidation Rules:1. Non-identical static models need to merge the same model (copied) without merging2, UV-free model can be combined with mesh baker duplicate mesh Baker will make an error in the production software need to merge3, using the same material model can be combined with different materials of the model cannot be merged4, the combined model map size must be 2 o
requires the program to manually go to start.For a task, you can pass an action when using its constructor (to pass a function with no arguments above), pass actionSecond, wait for a task to complete and get its execution resultsTo get execution results, we must construct a TaskCode
Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->NamespaceAlex.Net4MultiThread.MyTask {Internal ClassOwntask { Public Static voidMain () {TaskInt>T= NewTaskInt>(n=Su
The flashback table, in effect, is to quickly restore the data in the table to a previous point in time or to the system change SCN. To implement the flashback of the table, you need to use the Undo information related to the Undo table space, and you can understand this information by show PARAMETER Undo command. The user's modification of the table's data is recorded in the Undo Tablespace, which provides the basis for the data recovery provided by the table's flash-back.
Modified records are
Forum1.19 http://www.aka.org.cnChina Information Technology Forum-AKA1.20 http://www.lisoleg.netAgile feet (Linux Source Learning Group)1.21 http://www.linuxfans.org/China Linux Commune1.22 Http://www-900.ibm.com/developerWorks/cn/linuxIBM DeveloperWorks Linux Zone1.23 http://www.linuxaid.com.cnLinuxaid Technical Support Center1.24 http://lxr.linux.no/source/Cross-referencing Linux, can view the Linux kernel source code online1.25 http://www.linux.or
-repeatable reading means that a transaction reads the changed data that B transaction has committed. Assuming that a in the process of withdrawing money, b transfer to the account 100 yuan, a two read the balance of the account is inconsistent:
Time
Withdrawal transaction A
Transfer Transaction B
T1
Start a transaction
T2
Start a transaction
T3
Inquiry account balance is 1000 yuan
T4
Inquiry accoun
by the number of objects in the database 4 each SELECT The number of data tables for a statement 256256 the number of triggers per data table is limited by the number of objects in the database 4 limited by the number of objects in the database 4 the number of UNIQUE indexes per datasheet or constraints 249 nonclustered indexes and one clustered index 249 nonclustered indexes and one clustered index
1 network packet size is the size of the tabular Data Scheme (TDS) packet used for communicatio
with 0Save 900 1 # After 900 sec (min) If at least 1 key changedSave # After the SEC (5 min) If at least keys changedSave 10000 # After the SEC if at least 10000 keys changedStop-writes-on-bgsave-error YesRdbcompression Yes # compress Dump.rdbRdbchecksum Yes # check DUMP.RDBDbfilename Dump.rdb # dump file nameDir./# Dump file pathSlave-serve-stale-data YesSlave-read-only YesRepl-diskless-sync NoRepl-diskle
). The average time complexity of a bucket sort is linear, that is, O (n). Box sorting applies only to situations where the range of keyword values is small, otherwise the number of boxes required is too many to cause waste of storage space and calculation time. For example n=10, the sorted record keyword Ki takes a range of integers ranging from 0 to 99 (36,5,16,98,95,47, 32,36,48), using 100 boxes to sort the boxes. (When where m=n2, the time of the box is sorted O (m+n) =o (n2)).
Examp
automatically executes the Bgsave command every once in a while, and you can set multiple save conditions with the Save option, but the bgsage command is executed whenever either of these conditions is met
Columns such as:
Save 900 1
Save 300 10
Save 60 10000
So long as one of the following three conditions is met, the Bgsave command is executed
The server changed the database 1 times within 900 seconds
Th
of sliding windows.In particular, this should be the place where hog is most likely to produce anomalies. The picture below was originally a 900x600 900x600 900\times600 size, but I scaled it to 904x600 904x600 904\times600. This is to allow 904 of the range to slide out of the whole number of blocks, because at this time hog is using the default parameters, namely the block size 16x16 16x16 16\TIMES16, block step 8x8 8x8 8\times8.900−168=110.5
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