Applicable to: OpenHarmony SDK 3.2.3.5, stage model of API version 9
Run the hdc_std command to copy the .db, .db-shm, and .db-wal files from **/data/app/el2/100/database/Bundle name/entry/db/**, and then use the SQLite tool to open the files.
Run the hdc_std command to copy the .db, .db-shm, and .db-wal files in **/data/app/el2/100/database/*bundleName*/entry/db/**, and then use the SQLite tool to open the files.
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
The distributed data service (DDS), relational database (RDB) store, and preferences provided OpenHarmony have a lock mechanism. You do not need to bother with the lock mechanism during the development.
## What Is a Transaction in an RDB Store?
Applicable to: all versions
When a large number of operations are performed in an RDB store, an unexpected exception may cause a failure of some data operations and loss of certain data. As a result, the application may become abnormal or even crash.
A transaction is a group of tasks serving as a single logical unit. It eliminates the failure of some of the operations and loss of associated data.
## What Data Types Does an RDB Store Support?
Applicable to: OpenHarmony SDK 3.0 or later, stage model of API version 9
An RDB store supports data of the number, string, and Boolean types. The number array supports data of the Double, Long, Float, Int, or Int64 type, with a maximum precision of 17 decimal digits.
## How Do I View Database db Files?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
1. Run the **hdc_std shell** command.
2. Obtain the absolute path or sandbox path of the database.
The absolute path is **/data/app/el2/<userId>/database/<bundleName>**. The default **<userId>** is **100**.
To obtain the sandbox path, run the **ps -ef | grep hapName** command to obtain the process ID of the application.
The database sandbox path is **/proc/<Application process ID>/root/data/storage/el2/database/**.
3. Run the **find ./ -name "\*.db"** command in the absolute path or sandbox path of the database.
## How Do I Store Long Text Data?
Applicable to: OpenHarmony SDK 3.2.5.5, API version 9
- Preferences support a string of up to 8192 bytes.
- The KV store supports a value of up to 4 MB.
Reference: [Preference Overview](../database/database-preference-overview.md) and [Distributed Data Service Overview](../database/database-mdds-overview.md)
## How Do I Develop DataShare on the Stage Model
Applicable to: OpenHarmony SDK 3.2.5.5, API version 9
The DataShare on the stage model cannot be used with the **DataAbility** for the FA model. The connected server application must be implemented by using **DataShareExtensionAbility**.
Applicable to: OpenHarmony SDK 3.2.6.3, stage model of API version 9
## What If There is No Return Value or Error Captured After getAlbums Is Called?
Yes. **fileio.rmdir** deletes files recursively.
## How Do I Create a File That Does Not Exist?
Applicable to: OpenHarmony SDK 3.2.6.3, stage model of API version 9
Use **fileio.open(filePath, 0o100, 0o666)** to create a file that does not exist. The second parameter **0o100** means to create a file if it does not exist. The third parameter **mode** must also be specified.
## What If "call fail callback fail, code: 202, data: json arguments illegal" Is Displayed?
Applicable to: OpenHarmony SDK 3.2.6.3, stage model of API version 9
When the **fileio** module is used to copy files, the file path cannot start with "file:///".
## How Do I Read Files Outside the App Sandbox?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
If the input parameter of the **fileio** API is **path**, only the sandbox directory of the current app obtained from the context can be accessed. To access data in other directories, such as the user data, images, and videos, open the file as the data owner and operate with the file descriptor (FD) returned.
For example, to read or write a file in Media Library, perform the following steps:
1. Use **getFileAssets()** to obtain the **fileAsset** object.
2. Use **fileAsset.open()** to obtain the FD.
3. Use the obtained FD as the **fileIo** API parameter to read and write the file.
## What If the File Contains Garbled Characters?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
Read the file content from the buffer, and decode the file content using **util.TextDecoder**.
## What Should I Do If There is No Return Value or Error Captured After getAlbums Is Called?
Applicable to: OpenHarmony SDK 3.2.5.3, stage model of API version 9
The **ohos.permission.READ_MEDIA**permission is required for calling **getAlbums**, and this permission needs user authorization. For details, see OpenHarmony [Application Permission List](../security/permission-list.md).
The **ohos.permission.READ_MEDIA**is required for using **getAlbums()**. In addition, this permission needs user authorization. For details, see [OpenHarmony Permission List] (../security/permission-list.md).
1. Configure the required permission in the **module.json5** file.
...
...
@@ -34,3 +84,21 @@ The **ohos.permission.READ_MEDIA** permission is required for calling **getAlbum
})
}
```
## What Do I Do If the App Crashes When FetchFileResult() Is called Multiple Times?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
Each time after the **FetchFileResult** object is called, call **FetchFileResult.close()** to release and invalidate the **FetchFileResult** object .
## What if An Error Is Reported by IDE When mediaLibrary.getMediaLibrary() Is Called in the Stage Model?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
In the stage model, use **mediaLibrary.getMediaLibrary(context: Context)** to obtain the media library instance.
## How Do I Sort the Data Returned by mediaLibrary.getFileAssets()?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
Use the **order** attribute in **[MediaFetchOptions](../reference/apis/js-apis-medialibrary.md#mediafetchoptions7)** to sort the data returned.
