一朋友公司環境，因測試庫、生產庫錯連，造成大批量資料丟失，通過Oracle資料庫回收站方式已找回絕大部分資料，還有部分資料丟失， 檢視dg備端，發現備端歸檔都在，但沒有應用到資料庫裡。 可通過指定時間方式，先恢復資料庫到刪除之前的節點。 參考命令如下：

1. #示例為19c dg
2. #因操作不當，誤刪除了一個pdb，根據刪除時間，通過備端進行恢復
3. 2021-07-22T15:55:44.291222+08:00
4. drop pluggable database testpdb including datafiles
5. 2021-07-22T15:55:55.145297+08:00
6. Deleted file /u01/app/oracle/oradata/MYDB19C/testpdb/testpdb_user01.dbf
7. 2021-07-22T15:55:56.436102+08:00
8. Deleted file /u01/app/oracle/oradata/MYDB19C/testpdb/testpdb_temp01.dbf
10. #dg備端為mount狀態，通過rman恢復
11. RMAN> recover database until time "to_date('2021-07-22 15:51:00','YYYY-MM-DD HH24:MI:SS')";
13. Starting recover at 22-JUL-21
14. using target database control file instead of recovery catalog
15. allocated channel: ORA_DISK_1
16. channel ORA_DISK_1: SID=35 device type=DISK
18. starting media recovery
20. archived log for thread 1 with sequence 153 is already on disk as file /arch/1_153_1029107282.arc
21. archived log for thread 1 with sequence 154 is already on disk as file /arch/1_154_1029107282.arc
22. archived log for thread 1 with sequence 155 is already on disk as file /arch/1_155_1029107282.arc
23. archived log for thread 1 with sequence 156 is already on disk as file /arch/1_156_1029107282.arc
24. archived log for thread 1 with sequence 157 is already on disk as file /arch/1_157_1029107282.arc
25. archived log for thread 1 with sequence 158 is already on disk as file /arch/1_158_1029107282.arc
26. archived log for thread 1 with sequence 159 is already on disk as file /arch/1_159_1029107282.arc
27. archived log for thread 1 with sequence 160 is already on disk as file /arch/1_160_1029107282.arc
28. archived log for thread 1 with sequence 161 is already on disk as file /arch/1_161_1029107282.arc
29. archived log for thread 1 with sequence 162 is already on disk as file /arch/1_162_1029107282.arc
30. archived log for thread 1 with sequence 163 is already on disk as file /arch/1_163_1029107282.arc
31. archived log for thread 1 with sequence 164 is already on disk as file /arch/1_164_1029107282.arc
32. archived log file name=/arch/1_153_1029107282.arc thread=1 sequence=153
33. archived log file name=/arch/1_154_1029107282.arc thread=1 sequence=154
34. archived log file name=/arch/1_155_1029107282.arc thread=1 sequence=155
35. archived log file name=/arch/1_156_1029107282.arc thread=1 sequence=156
36. archived log file name=/arch/1_157_1029107282.arc thread=1 sequence=157
37. archived log file name=/arch/1_158_1029107282.arc thread=1 sequence=158
38. archived log file name=/arch/1_159_1029107282.arc thread=1 sequence=159
39. archived log file name=/arch/1_160_1029107282.arc thread=1 sequence=160
40. archived log file name=/arch/1_161_1029107282.arc thread=1 sequence=161
41. archived log file name=/arch/1_162_1029107282.arc thread=1 sequence=162
42. archived log file name=/arch/1_163_1029107282.arc thread=1 sequence=163
43. archived log file name=/arch/1_164_1029107282.arc thread=1 sequence=164
44. media recovery complete, elapsed time: 00:02:16
45. Finished recover at 22-JUL-21

檢查備端情況

1. --開啟資料庫
3. SQL> alter database open;
5. Database altered.
7. SQL> show pdbs
9. CON_ID CON_NAME OPEN MODE RESTRICTED
10. ---------- ------------------------------ ---------- ----------
11. 2 PDB$SEED READ ONLY NO
12. 3 TESTPDB MOUNTED
13. 4 MYPDB MOUNTED
14. --如果開啟recover，後續就刪除了testpdb
15. SQL> alter database recover managed standby database using current logfile disconnect from session;
17. Database altered.
19. SQL> show pdbs
21. CON_ID CON_NAME OPEN MODE RESTRICTED
22. ---------- ------------------------------ ---------- ----------
23. 2 PDB$SEED READ ONLY NO
24. 4 MYPDB MOUNTED

另，注意，Oracle19c 在mount資料庫時，dg備端會自動開啟recover模式，應用歸檔日誌。 alert日誌參考：

1. ARCc started with pid=64, OS id=88513
2. 2021-07-22T16:10:49.636837+08:00
3. MRP0 (PID:88499): Managed Standby Recovery starting Real Time Apply
4. 2021-07-22T16:10:49.672074+08:00
5. ARCd started with pid=65, OS id=88518
6. 2021-07-22T16:10:49.672676+08:00
7. Starting background process ARCe
8. 2021-07-22T16:10:51.903729+08:00
9. max_pdb is 8
10. 2021-07-22T16:10:55.411248+08:00
11. Starting background process ARCf
12. 2021-07-22T16:10:55.420715+08:00
13. ARCe started with pid=66, OS id=88524
14. 2021-07-22T16:10:57.850452+08:00
15. Starting background process ARCg
16. 2021-07-22T16:10:57.967273+08:00
17. ARCf started with pid=67, OS id=88528
18. 2021-07-22T16:11:01.664535+08:00
19. stopping change tracking
20. 2021-07-22T16:11:01.682638+08:00
21. MRP0 (PID:88499): Media Recovery Log /arch/1_151_1029107282.arc
22. 2021-07-22T16:11:02.562368+08:00
23. Completed: ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT NODELAY
24. 2021-07-22T16:11:03.176818+08:00
25. ARCg started with pid=68, OS id=88532
26. 2021-07-22T16:11:03.177282+08:00