.net关于控件绑定字段的数据类型
2010-10-05 02:38
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使用resetlogs的情况:
1)不完全介质恢复之后。
2)使用备份的控制文件进行恢复之后。
resetlogs作用:
1)归档当前重做日志,并清除联机重做日志的内容,重置日志序列号为1。
2)如果联机重做日志文件不存在,就创建它们。
3)重新初始化控制文件中有关联机重做日志与重做threads的元数据。
4)Updates all current datafiles and online redo logs and all subsequent archived redo logs with a new RESETLOGS SCN and time stamp.
在先前的版本中,oracle推荐使用resetlogs之后应该立即备份数据库;现在备份是可选的,可以跨resetlogs进行恢复,前提是最近备份以来的所有归档日志存在并且你拥有至少一份控制文件。
10gr2
The RESETLOGS option is always required after incomplete media recovery or recovery using a backup control file. Resetting the redo log does the following:
1)Archives the current online redo logs (if they are accessible) and then erases the contents of the online redo logs and resets the log sequence number to 1. For example, if the current online redo logs are sequence 1000 and 1001 when you open RESETLOGS,
then the database archives logs 1000 and 1001 and then resets the online logs to sequence 1 and 2.
2)Creates the online redo log files if they do not currently exist.
3)Reinitializes the control file metadata about online redo logs and redo threads.
4)Updates all current datafiles and online redo logs and all subsequent archived redo logs with a new RESETLOGS SCN and time stamp.
Because the database will not apply an archived log to a datafile unless the RESETLOGS SCN and time stamps match, the RESETLOGS prevents you from corrupting datafiles with archived logs that are not from direct parent incarnations of the current incarnation.
In prior releases, it was recommended that you back up the database immediately after the RESETLOGS. Because you can now easily recover a pre-RESETLOGS backup like any other backup, making a new database backup is optional. In order to perform recovery
through resetlogs you must have all archived logs generated since the last backup and at least one control file (current, backup, or created).
Figure 18-1 shows the case of a database that can only be recovered to log sequence 2500 because an archived redo log is missing. When the online redo log is at sequence 4000, the database crashes. You restore the sequence 1000 backup and prepare for complete
recovery. Unfortunately, one of your archived logs is corrupted. The log before the missing log contains sequence 2500, so you recover to this log sequence and open RESETLOGS. As part of the RESETLOGS, the database archives the current online logs (sequence
4000 and 4001) and resets the log sequence to 1.
You generate changes in the new incarnation of the database, eventually reaching log sequence 4000. The changes between sequence 2500 and sequence 4000 for the new incarnation of the database are different from the changes between sequence 2500 and sequence
4000 for the old incarnation. You cannot apply logs generated after 2500 in the old incarnation to the new incarnation, but you can apply the logs generated before sequence 2500 in the old incarnation to the new incarnation. The logs from after sequence 2500
are said to be orphaned in the new incarnation because they are unusable for recovery in that incarnation.
Figure 18-1 Creating a New Database Incarnation
1)不完全介质恢复之后。
2)使用备份的控制文件进行恢复之后。
resetlogs作用:
1)归档当前重做日志,并清除联机重做日志的内容,重置日志序列号为1。
2)如果联机重做日志文件不存在,就创建它们。
3)重新初始化控制文件中有关联机重做日志与重做threads的元数据。
4)Updates all current datafiles and online redo logs and all subsequent archived redo logs with a new RESETLOGS SCN and time stamp.
在先前的版本中,oracle推荐使用resetlogs之后应该立即备份数据库;现在备份是可选的,可以跨resetlogs进行恢复,前提是最近备份以来的所有归档日志存在并且你拥有至少一份控制文件。
10gr2
The RESETLOGS option is always required after incomplete media recovery or recovery using a backup control file. Resetting the redo log does the following:
1)Archives the current online redo logs (if they are accessible) and then erases the contents of the online redo logs and resets the log sequence number to 1. For example, if the current online redo logs are sequence 1000 and 1001 when you open RESETLOGS,
then the database archives logs 1000 and 1001 and then resets the online logs to sequence 1 and 2.
2)Creates the online redo log files if they do not currently exist.
3)Reinitializes the control file metadata about online redo logs and redo threads.
4)Updates all current datafiles and online redo logs and all subsequent archived redo logs with a new RESETLOGS SCN and time stamp.
Because the database will not apply an archived log to a datafile unless the RESETLOGS SCN and time stamps match, the RESETLOGS prevents you from corrupting datafiles with archived logs that are not from direct parent incarnations of the current incarnation.
In prior releases, it was recommended that you back up the database immediately after the RESETLOGS. Because you can now easily recover a pre-RESETLOGS backup like any other backup, making a new database backup is optional. In order to perform recovery
through resetlogs you must have all archived logs generated since the last backup and at least one control file (current, backup, or created).
Figure 18-1 shows the case of a database that can only be recovered to log sequence 2500 because an archived redo log is missing. When the online redo log is at sequence 4000, the database crashes. You restore the sequence 1000 backup and prepare for complete
recovery. Unfortunately, one of your archived logs is corrupted. The log before the missing log contains sequence 2500, so you recover to this log sequence and open RESETLOGS. As part of the RESETLOGS, the database archives the current online logs (sequence
4000 and 4001) and resets the log sequence to 1.
You generate changes in the new incarnation of the database, eventually reaching log sequence 4000. The changes between sequence 2500 and sequence 4000 for the new incarnation of the database are different from the changes between sequence 2500 and sequence
4000 for the old incarnation. You cannot apply logs generated after 2500 in the old incarnation to the new incarnation, but you can apply the logs generated before sequence 2500 in the old incarnation to the new incarnation. The logs from after sequence 2500
are said to be orphaned in the new incarnation because they are unusable for recovery in that incarnation.
Figure 18-1 Creating a New Database Incarnation
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