!9043 [翻译完成】#I5LY5Z

Merge pull request !9043 from Annie_wang/PR8017

en/application-dev/database/database-mdds-overview.md

-# Distributed Data Service Overview<a name="EN-US_TOPIC_0000001183067628"></a>
+# Distributed Data Service Overview
 
-The distributed data service \(DDS\) implements distributed database collaboration across devices for applications. Applications save data to distributed databases by calling the DDS APIs. The DDS isolates data of different applications based on a triplet of account, application, and database to ensure secure data access. The DDS synchronizes application data between trusted devices to provide users with consistent data access experience on different devices.
+The distributed data service (DDS) implements distributed database collaboration across devices for applications. 
 
-## Basic Concepts<a name="section17506141102520"></a>
+Applications save data to distributed databases by calling the DDS APIs. The DDS isolates data of different applications based on a triplet of account, application, and database to ensure secure data access. The DDS synchronizes application data between trusted devices to provide users with consistent data access experience on different devices.
+
+You do not need to care about the implementation of the database locking mechanism.
+
+## Basic Concepts
 
 -   **KV data model**
 
@@ -54,7 +58,7 @@ The distributed data service \(DDS\) implements distributed database collaborati
     The DDS provides the database backup capability. You can set  **backup**  to  **true**  to enable daily backup. If a distributed database is damaged, the DDS deletes the database and restores the most recent data from the backup database. If no backup database is available, the DDS creates one. The DDS can also back up encrypted databases.
 
 
-## Working Principles<a name="section315111581616"></a>
+## Working Principles
 
 The DDS supports distributed management of application database data in the OpenHarmony system. Data can be synchronized between multiple devices with the same account, delivering a consistent user experience across devices. The DDS consists of the following:
 
@@ -86,7 +90,7 @@ Applications call the DDS APIs to create, access, and subscribe to distributed d
 
 ![](figures/en-us_image_0000001183386164.png)
 
-## Constraints<a name="section95382010203311"></a>
+## Constraints
 
 -   The DDS supports the KV data model only. It does not support foreign keys or triggers of the relational database.
 -   The KV data model specifications supported by the DDS are as follows:

en/application-dev/database/database-relational-overview.md

-# RDB Overview<a name="EN-US_TOPIC_0000001231030607"></a>
+# RDB Overview
 
-The relational database \(RDB\) manages data based on relational models. With the underlying SQLite database, the RDB provides a complete mechanism for managing local databases. To satisfy different needs in complicated scenarios, the RDB offers a series of methods for performing operations such as adding, deleting, modifying, and querying data, and supports direct execution of SQL statements.
+The relational database (RDB) manages data based on relational models. With the underlying SQLite database, the RDB provides a complete mechanism for managing local databases. To satisfy different needs in complicated scenarios, the RDB offers a series of methods for performing operations such as adding, deleting, modifying, and querying data, and supports direct execution of SQL statements.
 
-## Basic Concepts<a name="section1063573420813"></a>
+You do not need to care about the implementation of the database locking mechanism.
 
--   **RDB**
+## Basic concepts
 
-    A type of database based on the relational model of data. The RDB stores data in rows and columns. An RDB is also called RDB store.
+- **RDB**
 
--   **Predicate**
+  A type of database created on the basis of relational models. The RDB stores data in rows and columns. A RDB is also called RDB store.
 
-    A representation of the property or feature of a data entity, or the relationship between data entities. It is mainly used to define operation conditions.
+- **Predicate**
 
--   **Result set**
+  A representation of the property or feature of a data entity, or the relationship between data entities. It is mainly used to define operation conditions.
 
-    A set of query results used to access the data. You can access the required data in a result set in flexible modes.
+- **Result set**
 
--   **SQLite database**
+  A set of query results used to access data. You can access the required data in a result set in flexible modes.
 
-    A lightweight open-source relational database management system that complies with Atomicity, Consistency, Isolation, and Durability \(ACID\).
+- **SQLite database**
 
+  A lightweight open-source relational database management system that complies with Atomicity, Consistency, Isolation, and Durability (ACID).
 
-## Working Principles<a name="section4810552814"></a>
+## Working Principles
 
-The RDB provides a common operation interface for external systems. It uses the SQLite as the underlying persistent storage engine, which supports all SQLite database features.
+The RDB provides common operation APIs for external systems. It uses the SQLite as the underlying persistent storage engine, which supports all SQLite database features.
 
-**Figure  1**  How RDB works<a name="fig1826214361535"></a>  
-![](figures/how-rdb-works.png "how-rdb-works")
+**Figure 1** How RDB works
 
-## Default Settings<a name="section176091243121218"></a>
+![how-rdb-works](figures/how-rdb-works.png)
 
--   The default database logging mode is write-ahead logging \(WAL\).
--   The default database flush mode is Full mode.
--   The default shared memory used by the OpenHarmony database is 2 MB.
+## Default Settings
 
-## Constraints<a name="section929813398308"></a>
+- The default RDB logging mode is Write Ahead Log (WAL).
+- The default data flushing mode is **FULL** mode.
+- The default size of the shared memory used by an OpenHarmony database is 2 MB.
 
--   A maximum of four connection pools can be connected to an RDB to manage read and write operations.
+## Constraints
 
--   To ensure data accuracy, the RDB supports only one write operation at a time.
+- A maximum of four connection pools can be connected to an RDB to manage read and write operations.
 
+- To ensure data accuracy, the RDB supports only one write operation at a time.

en/application-dev/database/database-storage-overview.md

-# Lightweight Data Store Overview<a name="EN-US_TOPIC_0000001230752103"></a>
+# Lightweight Data Store Overview
 
-Lightweight data store is applicable to access and persistence operations on the data in key-value pairs. When an application accesses a lightweight  **Storage**  instance, data in the  **Storage**  instance will be cached in the memory for faster access. The cached data can also be written back to the text file for persistent storage. Since file read and write consume system resources, you are advised to minimize the frequency of reading and writing persistent files.
+The lightweight data store is applicable to access and persistence of data in the key-value structure.
 
-## Basic Concepts<a name="section1055404171115"></a>
+After an application obtains a lightweight store instance, the data in the instance will be cached in the memory for faster access. The cached data can also be written back to the text file for persistent storage. Since file read and write consume system resources, you are advised to minimize the frequency of reading and writing persistent files.
 
--   **Key-Value data structure**
+You do not need to care about the implementation of the database lock mechanism.
 
-    A type of data structure. The key is the unique identifier for a piece of data, and the value is the specific data being identified.
+## Basic Concepts
 
--   **Non-relational database**
+- **Key-value structure**
 
-    A database not in compliance with the atomicity, consistency, isolation, and durability \(ACID\) database management properties of relational data transactions. The data in a non-relational database is independent.
+  A type of data structure. The key is the unique identifier for a piece of data, and the value is the specific data being identified.
 
+- **Non-relational database**
 
-## Working Principles<a name="section682631371115"></a>
+  A database not in compliance with the atomicity, consistency, isolation, and durability (ACID) properties of relational data transactions. The data in a non-relational database is independent.
 
-1.  When an application loads data from a specified  **Storage**  file to a  **Storage**  instance, the system stores the instance in the memory through a static container. Each file of an application or process has only one  **Storage**  instance in the memory, till the application removes the instance from the memory or deletes the  **Storage**  file.
-2.  When obtaining a  **Storage**  instance, the application can read data from or write data to the instance. The data in the  **Storage**  instance can be flushed to its  **Storage**  file by calling the  **flush**  or  **flushSync**  method.
+## Working Principles
 
-**Figure  1**  How lightweight data store works<a name="fig1657785713509"></a>  
+1. An application can load data from a specified **Storage** file to a **Storage** instance. The system stores the instance in the memory through a static container. Each file of an application or process has only one **Storage** instance in the memory, till the application removes the instance from the memory or deletes the **Storage** file.
+2. When obtaining a **Storage** instance, the application can read data from or write data to the instance. The data in the **Storage** instance can be flushed to its **Storage** file by calling the **flush** or **flushSync** method.
 
+**Figure 1** Working mechanism
 
 ![](figures/en-us_image_0000001199139454.png)
 
-## Constraints<a name="section17243172883219"></a>
-
--   **Storage**  instances are loaded to the memory. To minimize non-memory overhead, the number of data records stored in a  **Storage**  instance cannot exceed 10,000. Delete the instances that are no longer used in a timely manner.
--   The key in the key-value pairs is of the string type. It cannot be empty or exceed 80 characters.
--   If the value in the key-value pairs is of the string type, it can be empty or contain a maximum of 8192 characters.
+## Constraints
 
+- **Storage** instances are loaded to the memory. To minimize non-memory overhead, the number of data records stored in a **Storage** instance cannot exceed 10,000. Delete the instances that are no longer used in a timely manner.
+- The key in the key-value pairs is of the string type. It cannot be empty or exceed 80 bytes.
+- The value of the string type can be empty, but cannot exceed 8192 bytes if not empty.