Description of % a in RMAN backup FORMAT the oracle document describes % a as follows: [SQL] % a Specifies the activation ID of the database. rman backup and save, query % a [SQL] RMAN> backup tablespace users format '/home/oracle/think _ % a'; www.2cto.com. From this, we can see that % a is: 790774120 query x $ kccdi [SQL] sys @ ORCL> SELECT didbn, dirlc, dirlc_ I FROM x $ kccdi; didbn dirlc DIRLC_ I --------- hour ---------- ORCL 08/08/2012 11:28:40 790774120, % a is the DIRLC_ I query v $ database_inc. Arnation [SQL] sys @ ORCL> select INCARNATION #, RESETLOGS_TIME, RESETLOGS_ID from v $ database_incarnation; INCARNATION # RESETLOGS_TIME RESETLOGS_ID ------------ then ---------- 1 minute 19:09:40 562360180 2 minute 16:40:15 788719215 3 minute 10:35:10 790770910 4 minute 11:28:40 790774120 www.2cto.com from this, we can see that % a, resetlogs_id and dirlc_ I are the same. RESETLOGS_ID is determined by RESETLOGS_TIME. Therefore, the three "same-breath connection technology ". In fact, the value of this RESETLOGS_ID can also be found in the V $ ARCHIVED_LOG view. This value corresponds to % r in the archive log format. % R official documentation explanation: [SQL] resetlogs ID that ensures unique names are constructed for the archived log files should SS multiple incarnations of the database if incomplete recovery is performed, this variable is very important. Query v $ archived_log [SQL] sys @ ORCL> select first_time, name from v $ archived_log where first_time = '2017/08 11:28:40 '; www.2cto.com FIRST_TIME NAME ------------------- 11:28:40/u01/app/oracle/flash_recovery_area/ORCL/archivelog/2012_08_08/o1_mf_1_1 _ 2017467pw _. according to arc, % r is 2017467pw. Summary: % a, resetlogs_id, dirlc_ I, and % r are the "Birthdays" of oracle database ". author: linwaterbin