BACKUP DATABASE PLUS ARCHIVELOG; 做了什么

You can add archived redo logs to a backup of other files by using the BACKUP ... PLUS ARCHIVELOG clause. Adding BACKUP ... PLUS ARCHIVELOG causes RMAN to do the following:
·Runs the ALTER SYSTEM ARCHIVE LOG CURRENT command.
·Runs BACKUP ARCHIVELOG ALL. Note that if backup optimization is enabled, then RMAN skips logs that it has already backed up to the specified device.
·Backs up the rest of the files specified in BACKUP command.
·Runs the ALTER SYSTEM ARCHIVE LOG CURRENT command.
Backs up any remaining archived logs generated during the backup.
This guarantees that datafile backups taken during the command are recoverable to a consistent state.

backup database plus archivelog;
=
'alter system archive log current'
backup arcvhielog all;
backupo database all;
'alter system archive log current'
backup archvielog all;
从9i开始，就会在备份datafile 之前和之后自动做一次'alter system archive log current'

restore validate 和 crosscheck 的区别是什么？

先来看看官方文档上的说法：

    restore validate：Lets RMAN decide which backup sets, datafile copies, and archived logs need to be restored, and then scans them to verify their contents. No files are restored. Use VALIDATE to verify that the backups required to restore the specified files are intact and usable.

    用来判断 备份集是否可用

    crosscheck：To verify the status of backups and copies recorded in the RMAN repository against media such as disk or tape. The CROSSCHECK command only processes files created on the same device type as the channels running the crosscheck.

    用来检查 备份集 或对应的文件是否存在

    resetlogs 都做了什么：

    1.  Creates the online redo log files if they do not currently exist.
    2.  Reinitializes the control file metadata about online redo logs and redo threads to start generating sequence #1.
    3.  Updates all current datafiles and online redo logs with a new RESETLOGS SCN and time stamp.