## 4.2.15.10.4  Read Archived Data
Applications can use the ADK read API to read the data which is contained in an archive file stored in an external storage system.
There are two possible ways to access the data:
- Read the data for entire archive files sequentially
- Read the data by index access
To optimize the reading access on archive files, an index solution can be established in the application. For an index-based read access, the archive key and the offset of a data object are needed. ADK API provides this information within methods IF\_ARCH\_DELETE\_API-&gt;GET\_NEXT\_DATA\_OBJECT and IF\_ARCH\_READ\_API-&gt;GET\_NEXT\_DATA\_OBJECT .
A typical index-based solution needs a transparent table containing columns for application attributes, a column for the archive key and a column for the offset. The archive key is the ID of the archive file, which contains the application attribute. The offset is the offset in the archive file at which the data for the application attribute starts. Usually, the initial construction of an archive index will be established by deleting archived data from the database [page 1493]. In case the index should be constructed at a later point in time, the ADK read API can be used to determine archive key and offset (returned by method IF\_ARCH\_READ\_API-&gt;GET\_NEXT\_DATA\_OBJECT ).
## CL\_ARCH\_READ\_API (API to read archived data)
| Method                                                                           | Parameter                                 | Description                                             |
|----------------------------------------------------------------------------------|-------------------------------------------|---------------------------------------------------------|
| GET_FILES_TO_READ                                                                | Importing: IT_DATE_SELECTION              | Range on dates on which archive files have been created |
| Selection of archiving sessions and files                                        | Importing: IT_USER_SELECTION              | Range on users which have created ar- chive files       |
|                                                                                  | Importing: IT_ARCHIVING_OBJECT            | Archiving object which will be used                     |
|                                                                                  | Return- ing: RT_ARCHIVING_FILE_ATTRIBUTES | Archiving sessions' attributes                          |
| GET_INSTANCE                                                                     | Importing: IV_ARCHIVING_OBJECT            | Nameof the archiving object which will be used          |
| Returns an instance of the de- lete API. Reference to interface IF_ARCH_READ_API | Importing: IV_ARCHIVING_SESSION           | Sessions of the archiving object which will be used     |
|                                                                                  | Importing: IT_ARCHIVE_KEY                 | Archive key for which data should be read               |
|                                                                                  | Returning: RO_READ_INSTANCE               | Instance of the read API for further processing         |
## IF\_ARCH\_READ\_API (Interface to read archived data)
| Method                                                      | Parameter                       | Description                                             |
|-------------------------------------------------------------|---------------------------------|---------------------------------------------------------|
| GET_DATA_RECORDS Read records by structure from the         | Importing: IV_RECORDS_STRUCTURE | Nameof the structure of all data re- cords in the table |
| cur- rent data object                                       | Exporting: EV_DATA_RECORDS      | Table containing the data records                       |
| GET_NEXT_DATA_OBJECT Read data object from the archive file | Exporting: EV_ARCHIVE_KEY       | Archive key according to archive man- agement           |
|                                                             | Exporting: EV_END_OF_FILE       | Boolean values: TRUE (='X') FALSE (= ' ')               |
|                                                             | Exporting: EV_ARCHIVING_SESSION | Sessions of the archiving object which will be used     |
|                                                             | Exporting: EV_OBJECT_OFFSET     | Offset of data object in the archive                    |
## CLOSE
Open archive files will be closed
As mentioned before, there are two different ways to acceess the data. A typical procedure for the sequential read access would be as follows:
1. Determine files which are available for evaluation by using the method
2. CL\_ARCH\_READ\_API=&gt;GET\_FILES\_TO\_READ , with filter options on creating user and creation date of the archive file.
2. Create an instance of the read API and open the archiving read session for one of the selected archive files by using the method CL\_ARCH\_READ\_API=&gt;GET\_INSTANCE .
3. Open the next data object with the method GET\_NEXT\_DATA\_OBJECT . If the method returns EV\_END\_OF\_FILE = TRUE ('X') , continue with step 6.
4. Read the data with the method GET\_DATA\_RECORDS .
5. Continue with the next data object. See step 3.
6. Finish the read operation by calling method CLOSE .
A typical flow of the index-based read access would be as follows:
1. Determine the archive key and the offset of the data object by selecting the relevant entry from your index table.
2. Create an instance of the read API and open the archiving read session for the data object by using the method CL\_ARCH\_READ\_API=&gt;GET\_INSTANCE\_BY\_OFFSET .
3. Read the data by using the method GET\_DATA\_RECORDS .
4. Finish the read operation by calling method CLOSE .
An example code for the index-based read operation:
```
 Sample Code CONSTANTS: lc_object TYPE if_arch_api_types=>ty_object_name VALUE 'MY_OBJECT'. DATA: lt_data TYPE STANDARD TABLE OF my_item_table. DATA: lt_index TYPE STANDARD TABLE OF my_index_table. " let's assume, we want to read the archived bookings for flight AA/0040 on 20010110 TRY. " get archive key and offset for the given flight from the index table SELECT * FROM my_index_table WHERE carrid = 'AA' AND connid = '0040' AND fldate = '20010110' INTO TABLE @lt_index. SORT lt_index BY archive_key DESCENDING. READ TABLE lt_index ASSIGNING FIELD-SYMBOL(<ls_index>) INDEX 1. IF NOT <ls_index> IS ASSIGNED. RETURN. ENDIF. " open a read instance for the archive key and offset found DATA(lo_read) = cl_arch_read_api=>get_instance_by_offset ( iv_archiving_object = lc_object iv_archive_key = <ls_index>-archive_key iv_object_offset = <ls_index>-archive_offset ). " get all archived booking entries for this flight lo_read->get_data_records( EXPORTING iv_record_structure = 'MY_ITEM_TABLE1' IMPORTING et_data_records = lt_data ). " close the read instance lo_read->close( ).
```