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concurrency problems for one or more transactions Concurrency Runtime :Summarizes the first category of missing updates, dirty reads, virtual reads, non-repeatable reads, and second-class missing updates.1, the first category of missing updates:

Hibernate uses object identifiers (OIDs) to establish correspondence between objects in memory and records in database tables, and the OID of the object corresponds to the primary key of the database. To ensure the uniqueness and immutability of the

First,hibernate the policy for accessing persisted class properties :The Access property in the element is used to specify how hibernate accesses persisted class properties.　　the common way is as follows :1, Property: Default value. Hibernate

Although the file system can be mounted manually, but each time the manual mount will be cumbersome, the purpose of the boot mount is to achieve automatic file system mount.First, boot mount:/etc/fstab and/etc/mtabThis is done primarily by modifying

Mounting is the operation of combining a file system with a directory. A mount point is a directory, which is the entry into a partition or file system.I. Precautions before MOUNTING:1, a single file system should not be repeatedly mounted on

This article only serves as a trap.One, view the disk and directory capacity: DF duDF: Lists the overall disk usage for the file system.Du: Evaluating the disk usage of the file system (commonly used to estimate the capacity of the catalog)Ii.

Common commands: Cat, TAC, NL, more, less, head, tail, OD ...First, directly view the contents of the file: Cat, TAC, NL 1. cat [-abentv] File nameParameter description:-N: Prints the travel number, along with a blank line number.-B: Prints the

Did a cat factory very classic front-end pen test questions, solved the two columns have been on the understanding of the layout of too few problems. The title requirement is right aside fixed width 200px, left content adaptive. Originally directly

A few days of ML, tried a lot of new features, but finally found, or this let tingting call my master's function most refreshing First, in the settings-notification, all the cue styles are set to: hint Second, in the settings-dictation and

The topic that we share today is Javascript&qa⼯. See this topic, may be asked: the front end of the development is OK, the rest of the test on the line, where still need to care about these? But in fact, testing is a very important aspect of

1, how to get Database link connection in JDBC? Driver is an interface: The database vendor must provide an interface for implementation. from which the database connection can be obtained.The database connection can be obtained through the Driver

First, map set (set): not sorted, no duplicates.　　Instance Code :? 1 2 3 4 set name="images" table="IMAGES" lazy="true" > 　　key column="CUSTOMER_ID" /> 　　column="FILENAME" type="string" not-null="true"/> set>

First, the principle of the use of composition relations :Minimizing the number of database tables and foreign key references between tables, without causing data redundancy, is a time-consuming operation to establish a connection to multiple tables.

Hibernate takes a mapping type as a bridge between Java type and SQL type, corresponding to the type attribute.There are two types: the built-in mapping type and the custom mapping type.One, built-in mapping type :1,JaVA basic types of Hibernate

1. persist entity domain objects directly through the JDBC API :A, java.sql Common interfaces and classes:DriverManager: Driver Manager, responsible for creating database connections.Connection: Represents a database connection.Statement:

One, the script file query:1, command format: which [-a] command; -A: Lists all, not only the first.Example: which ifconfig;Note: Because different user paths are different, there may be differences in the results.Second, the name of the search:1,

One, relative path and absolute path:A, Absolute path: The path that is written by the root directory/start, for example/usr/share/docB, relative path: a path that is not written by the root directory/start.Second, the relevant operation of the

First, the relationship between boot sector and Super BLOCK:1. Boot sector is used to store the boot loader, which occupies 1024 bytes.2, super block size is also 1024 bytes.3, if the block size is 1k, then the boot sector and Super block each

First, Mknod: Set the device codeIn Linux, all devices are represented by files, and the files are judged by major and minor values.Major is the main device code, minor is the device code (need to query), the example is as

After the partition is complete, the disk is formatted to generate the file system.Command format: MKFS [-T file system format] device file name Example: Mkfs-t Ext3/dev/sda6;　　The lack of the above command is not able to specify the volume label of