本文解析了Oracle数据库中控制文件和在线重做日志文件的位置管理机制，详细介绍了db_create_online_log_dest_n、control_files及db_recovery_file_dest等参数的作用，并讨论了它们之间的优先级关系及其对文件多路复用的影响。
三个参数对 redo、control文件位置的影响：
1. 位置优先级：【control_files 初始化参数】 > db_create_online_l og_dest_n >
db_recovery_file_dest<wbr><wbr> >=<wbr><wbr> db_create_file_dest<br> 此处的等于号比较有意思：如果没有 db_create_online_log_dest_n,而存在db_create_file_dest 时，db_recovery_file_dest 就相当db_create_online_log_dest_2，<br> db_create_file_dest 则相当于db_create_online_log_dest_1.<br><br><br> NOTE:<br> DB_CREATE_ONLINE_LOG_DEST_n (where n = 1, 2, 3, ... 5) specifies the default<br> location for Oracle-managed control files and online redo logs. If more than one<br> DB_CREATE_ONLINE_LOG_DEST_n parameter is specified, then the control file or online<br> redo log is multiplexed across the locations of the other<br> DB_CREATE_ONLINE_LOG_DEST_n parameters. One member of each online redo log is<br> created in each location, and one control file is created in each location.<br> Specifying at least two parameters provides greater fault tolerance for the<br> control files and online redo logs if one of the locations should fail.<br> If a file system directory is specified as the default location, then the<br> directory must already exist; Oracle does not create it. The directory must have<br> appropriate permissions that allow Oracle to create files in it . Oracle generates<br> unique names for the files, and a file thus created is an Oracle-managed file.<br> db_recovery_file _dest 参数启用 redo、control、rman backups、archived logs、flashback<br> logs 文件的 omf 管理,类似的 db_create_online_log_dest_n 参数启用 redo、control 的 omf<br> 管理,从中我们也可以看出 redo、control 文件的重要性！！<br><br><br><br><br> 2. redo 文件的多路复用<br> 通常应该通过指定 db_create_online_log_dest_n 来达到该目的！<br> 3. 如果三个参数指定相同的值会怎样？自己猜吧 ：）<br><br> 4. omf 文件的命名规则<br> <_dest_参数路径>/<db_unique_name_or_db_name>/<datafile>/o1_mf_%t_%u_.dbf<br><br></wbr></wbr></wbr></wbr>
1. 位置优先级：【control_files 初始化参数】 > db_create_online_l og_dest_n >
db_recovery_file_dest<wbr><wbr> >=<wbr><wbr> db_create_file_dest<br> 此处的等于号比较有意思：如果没有 db_create_online_log_dest_n,而存在db_create_file_dest 时，db_recovery_file_dest 就相当db_create_online_log_dest_2，<br> db_create_file_dest 则相当于db_create_online_log_dest_1.<br><br><br> NOTE:<br> DB_CREATE_ONLINE_LOG_DEST_n (where n = 1, 2, 3, ... 5) specifies the default<br> location for Oracle-managed control files and online redo logs. If more than one<br> DB_CREATE_ONLINE_LOG_DEST_n parameter is specified, then the control file or online<br> redo log is multiplexed across the locations of the other<br> DB_CREATE_ONLINE_LOG_DEST_n parameters. One member of each online redo log is<br> created in each location, and one control file is created in each location.<br> Specifying at least two parameters provides greater fault tolerance for the<br> control files and online redo logs if one of the locations should fail.<br> If a file system directory is specified as the default location, then the<br> directory must already exist; Oracle does not create it. The directory must have<br> appropriate permissions that allow Oracle to create files in it . Oracle generates<br> unique names for the files, and a file thus created is an Oracle-managed file.<br> db_recovery_file _dest 参数启用 redo、control、rman backups、archived logs、flashback<br> logs 文件的 omf 管理,类似的 db_create_online_log_dest_n 参数启用 redo、control 的 omf<br> 管理,从中我们也可以看出 redo、control 文件的重要性！！<br><br><br><br><br> 2. redo 文件的多路复用<br> 通常应该通过指定 db_create_online_log_dest_n 来达到该目的！<br> 3. 如果三个参数指定相同的值会怎样？自己猜吧 ：）<br><br> 4. omf 文件的命名规则<br> <_dest_参数路径>/<db_unique_name_or_db_name>/<datafile>/o1_mf_%t_%u_.dbf<br><br></wbr></wbr></wbr></wbr>
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