Oracle参数篇

1. ARCHIVE_LAG_TARGET forces a log switch after the specified amount of time elapses.有效值为0（disabled）或 [ 60,7200 ]

2. SEC_PROTOCOL_ERROR_FURTHER_ACTION specifies the further execution of a server process when receiving bad packets from a possibly malicious client.SEC_PROTOCOL_ERROR_FURTHER_ACTION = { CONTINUE | (DELAY,integer) | (DROP,integer) }

3. ASM_POWER_LIMIT  specifies the maximum power on an Automatic Storage Management instance for disk rebalancing. The higher the limit, the faster rebalancing will complete. Lower values will take longer, but consume fewer processing and I/O resources.

4. DB_FILE_MULTIBLOCK_READ_COUNT DB_FILE_MULTIBLOCK_READ_COUNT is one of the parameters you can use to minimize I/O during table scans. It specifies the maximum number of blocks read in one I/O operation during a sequential scan. The total number of I/Os needed to perform a full table scan depends on such factors as the size of the table, the multiblock read count, and whether parallel execution is being utilized for the operation.

5. SGA_MAX_SIZE SGA_MAX_SIZE specifies the maximum size of the SGA for the lifetime of the instance.On 64-bit platforms and non-Windows 32-bit platforms, when either MEMORY_TARGET or MEMORY_MAX_TARGET is specified, the default value of SGA_MAX_SIZE is set to the larger of the two parameters. This causes more address space to be reserved for expansion of the SGA.

6. OPEN_CURSORS OPEN_CURSORS specifies the maximum number of open cursors (handles to private SQL areas) a session can have at once. You can use this parameter to prevent a session from opening an excessive number of cursors.

7. DB_FLASHBACK_RETENTION_TARGET DB_FLASHBACK_RETENTION_TARGET specifies the upper limit (in minutes) on how far back in time the database may be flashed back. How far back one can flashback a database depends on how much flashback data Oracle has kept in the fast recovery area.

8. LOCAL_LISTENER LOCAL_LISTENER specifies a network name that resolves to an address or address list of Oracle Net local listeners (that is, listeners that are running on the same machine as this instance). The address or address list is specified in the TNSNAMES.ORA file or other address repository as configured for your system.语法：LOCAL_LISTENER = network_name，默认值是(ADDRESS = (PROTOCOL=TCP)(HOST=hostname)(PORT=1521)) where hostname is the network name of the local host.

它填的是TNSNAMES.ORA中的网络字符串，通过该网络字符串来映射本地监听器的地址，若TNSNAMES.ORA文件中内容如下：

TEST3 =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = node2.being.com)(PORT = 1523))
    )
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = sz.being.com)
    )
  )

TEST2 =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = node2.being.com)(PORT = 1522))
    )
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = sz.being.com)
    )
  )

TEST1 =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = node2.being.com)(PORT = 1521))
    )
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = sz.being.com)
    )
  )

倘若两个端口1522,1523对应的监听器已启动，若我将LOCAL_LISTENER设置为以下值：SQL> alter system set local_listener='TEST3';则我用TEST2登陆数据库，会报以下错误：

[oracle@node2 admin]$ sqlplus scott/tiger@test2
ERROR:
ORA-12514: TNS:listener does not currently know of service requested in connect
descriptor

Enter user-name: 

但是用TEST3，即sqlplus scott/tiger@test3会成功登陆，反之亦然。

如果我想既能用TEST2登陆又能用TEST3登陆，则LOCAL_LISTENER必须设置为以下值：SQL>  alter system set local_listener='TEST2','TEST3';

注意：1. 若LOCAL_LISTENER为空，则默认映射1521端口

2. 即便LOCAL_LISTENER设置为 local_listener='TEST2','TEST3'，TEST1仍能成功登陆，即1521端口是默认的。