sra levels

no active transaction, Then press Transactiondefinition.propagation_required property to perform 4. Isolation level of spring transaction 1. Isolation_default: This is a platfromtransactionmanager default isolation level that uses the default transaction isolation level of the database. The other four levels of isolation from JDBC correspond to 2. Isolation_read_uncommitted: This is the lowest isolation level for a transaction, which allows an exte

Experimental Purpose In a programming language, you can compare code writing in different programming styles, or generate assembly code from a compiler by using different compilers and compilation optimization parameters, and statically analyze the efficiency of the generated assembly code. experimental platform, tools Under the Windows platform, use the VC6.0 tool. Experimental design Optimized comparison of redundant code by the same compiler at different

If you use 64-bit integers and 32-bit integers, how long does it take to represent subtle levels of time? #define __stdc_format_macros #include [Winlin@dev6 temp]$ g++ test.cpp-o int64-day [Winlin@dev6 temp]$./int64-day 64bits=18446744073709551615us, 18446744073709551ms, 18446744073709s, 5124095576hour, 213503982day, 584942year 32bits=4294967295us, 4294967ms, 4294s, 1hour, 0day, 0year If it is used to denote milliseconds: #define __stdc_format

already exists, the existing transaction is suspended. 5. Propagation_not_supported: Always executes in a non-transactional manner and suspends any existing transactions. 6. Propagation_never: Always executes in a non-transactional manner, and throws an exception 7 if there is an active transaction . Propagation_nested: If an active transaction exists, it is run in a nested transaction. If there is no active transaction, press the Transactiondefinition.propagation_required property to ex

utilization 2. Reduce waiting timeTransaction scheduling: recoverable scheduling; no cascade height:Technical means of concurrency control dependencies: Lock time Stamp Multi-version and snapshot isolationSTART TRANSACTION | Begin: Start a transaction SQL SQLCommit: SubmitROLLBACK: Rolling backIf the transaction is not explicitly started: autocommit: Can achieve automatic submission, each operation is submitted directly; Recommendation: Explicitly use transactions, and turn off autocommit;Sav

over, in order to deepen understanding and memoryIf you have a foundation, you can choose chapters to learn according to your needs.2.3. Instructor Recommendations1. Be sure to follow the course to practice, think more, and work more together on the scene.2. It is a very good learning habit to watch videos and make some records and notes on the side.3. Be sure not to rely too much on video, to learn to read the API and use Baidu, learn to think, learn extrapolate4. Finally, I wish you to learn

: Use the primary key (primary key) and index as criteria to query. Do not use join. Do not use aggregate functions (aggregation). Perform heavy queries (housekeeping queries) only in replicas (replica), such as Business Intelligence (BI), data exploration, and so on, as far as possible, not on the main library (master database). We're going to dive into another blog about live migration (live migrations) and Application layer transactions (applicative transactions).

PostgreSQL two types of transaction isolation levels:Read Committed: The default isolation level in PostgreSQL. When a transaction runs at this isolation level, a select query can see only the data that was committed before the query was started and never see uncommitted data or changes made by other parallel transaction commits while the query was executing. If two transactions are being updated on the same tuple, the second update transaction waits for the first update transaction to commit or

XACT_ABORT on option is turned on: 2. Rollback According to user's settings (ROLLBACK) This approach is more flexible, and developers can customize what happens to rollback, which is the way to judge using a try Catch statement and @ @ERROR. Understanding Consistency (consistency) Consistency, that is, the integrity constraints of the database are not compromised until the transaction is started and after the transaction ends. Consistency is divided into two

Article Source: http://blog.chinaunix.net/uid-22746363-id-383989.htmlLinux System has 7 runlevel (runlevel)RunLevel 0: System down state, system default RunLevel cannot be set to 0, otherwise it will not start normallyRunLevel 1: Single User working status, root privilege, for system maintenance, remote login ForbiddenRunLevel 2: Multi-User State (no NFS)RunLevel 3: Full multiuser State (with NFS), enter console command line mode after loginRun Level 4: System not used, reservedRun level 5:x11 c

RAID It means a redundant array of inexpensive disks (redundant array of inexpensive Disks), but now it is known as a redundant array of independent disks (redundant array of independent Drives). Earlier a very small disk was very expensive, but now we can buy a larger disk cheaply. Raid is a collection of disks that are put together to become a logical volume. AID contains a group or a collection or even an array. Use a set of disk-combined drives to compose a RAID array or RAID set. Connect at

transactions that read data do not prevent other transactions from writing to the data. transactions that write data do not prevent SNAPSHOT transactions from reading data. in the rollback phase of database recovery, if you attempt to read data that is locked by another transaction that is being rolled back, the SNAPSHOT transaction will request a lock. the SNAPSHOT transaction is blocked until the transaction has finished rolling back. when a transaction is authorized, the lock is released im

RAID It means a redundant array of inexpensive disks (redundant array of inexpensivedisks), but now it is known as a redundant array of independent disks (redundant array of independent Drives). Earlier a very small disk was very expensive, but now we can buy a larger disk cheaply. Raid is a collection of disks that are put together to become a logical volume. AID contains a group or a collection or even an array. Use a set of disk-combined drives to compose a RAID array or RAID set. Connect at

Class one or four isolation level The SQL standard defines 4 classes of isolation, including specific rules that define which changes are visible inside and outside the transaction and which are not. The low-level isolation level generally supports higher concurrency processing and has lower system overhead. Read uncommitted(Reading uncommitted content) At this isolation level, all transactions can see the execution results of other uncommitted transactions. This isolation level is rarely use

Isolation levels in SQL Server control the locking works between transactions.SQL Server supports the following isolation levels Read UNCOMMITTED Read Committed (the default) Repeatable Read Serializable Snapshot Before I run through each of the these in detail if want to create a new database to run the examples, run the followingScript on the new database to create the sample

associated with it is closed, the execution is considered complete.For a stored procedure or other statement that returns multiple results when all the ResultSet objects associated with it are closed, all update count (the number of rows affected by a statement operation such as Update,delete) and the output parameter (the stored procedure outputs parameters) is considered executed after it has been acquired.B. When Auto-commit is false, each transaction must appear to be committed by calling t

level generally supports higher concurrency processing and has lower system overhead. READ UNCOMMITTED (reading uncommitted content) At this isolation level, all transactions can see the execution results of other uncommitted transactions. This isolation level is rarely used for practical purposes because it does not perform much better than other levels. Reading uncommitted data is also called dirty Read (Dirty read). Read Committed (reading subm

In addition to applying heading styles, specifying outline levels for headings can also be a quick way to create a table of contents. The steps are as follows: 1. Perform "view" → "toolbar" → "outline" to display the Outline toolbar. 2. Place the insertion point in the first heading that you want to appear in the table of contents. 3. On the Outlining toolbar, click to open the Outline level drop-down box to select an outline level for this title.

Original posts: http://blog.csdn.net/tolcf/article/details/49283575Defined:In the database operation, in order to effectively guarantee the correctness of the concurrent read data, the transaction isolation level is proposed.There are 4 isolation levels for database transactions, from low to high to read uncommitted (unauthorized read, read UNCOMMITTED), Read committed (authorization read, read commit), REPEATABLE read (repeatable read), Serializable

Excerpt: https://www.cnblogs.com/snsdzjlz320/p/5761387. HTML-------------------------------------------------------This article is more detailed, especially readcommitted and Repertableread.the difference between readcommitted and RepeatableRead, is that readcommitted can read his uncommitted and the person has submitted, Repearableread can only read their uncommitted with the transaction opened before it was submitted by the person,once the transaction is opened, the content that it commits is