AUTOMATIC MANAGEMENT AND ONLINE CAPABILITIES in Font

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You can confirm the name of your new ASM instance with the following query: SQL> SELECT instance_name FROM v$instance; INSTANCE_NAME ---------------+ASM SQL> If you run the LSNRCTL STATUS command from the command line, you ll see that the listener has automatically registered the new ASM instance: Service "+ASM" has one instance(s). You can check the newly created ASM instance processes in the following way: [+ASM] $ ps ef | grep asm oracle 3201 1 0 Jul 3 (LOCAL=YES) (ADDRESS=(PROTOCOL=beq))) oracle 11977 1 0 12:56 oracle 11979 1 0 12:56 oracle 11981 1 0 12:56 oracle 11985 1 0 12:56 oracle 11973 1 1 12:56 oracle 11987 1 0 12:56 oracle 11989 1 0 12:56 oracle 11991 1 0 12:56 oracle 11995 1 0 12:56 [+ASM] $ 0:00:00 oracleasm+ (DESCRIPTION = 0:00: 0:00: 0:00: 0:00: 0:00: 0:00: 0:00: 0:00: 0:00: 05 02 02 02 02 03 02 02 02 asm_pmon_+asm asm_psp0_+asm asm_mman_+asm asm_dbw0_+asm asm_lgwr_+asm asm_ckpt_+asm asm_smon_+asm asm_rbal_+asm asm_gmon_+asm

All the background processes shown in the preceding output are standard Oracle Database 10g processes, with the exception of a couple of background processes specific to an ASM instance. The following section explains the important ASM-specific background processes.

You don t need to back up an ASM database, since you don t have any physical ASM data files to back up! Tip This is also why you can t use the MOUNT and OPEN options while starting an ASM instance. All ASM metadata is either stored in the SGA while the ASM instance is running or stored on the disk groups and mirrored, to provide high availability.

An ASM instance uses several regular Oracle background processes, such as SMON, PMON, and LGWR. In addition, ASM utilizes two new ones: ASM rebalance master (RBAL) and ASM rebalance (ARBn). The RBAL process coordinates disk activity, and the ARBn processes perform the rebalancing work, which can include moving data extents. In addition to ASM s RBAL and ARBn, any Oracle database instance that uses ASM will have two ASM-related background processes: RBAL and ASM background (ASMB). RBAL performs global opens of the disks that are part of the ASM disk group, and ASMB connects to the ASM instance as a foreground process and links the ASM instance and your database instance, sending information such as notifications when a data file is created or deleted, and when statistics are updated. You can use the OEM Database Control to manage an ASM instance. Its main page shows your ASM instance s status. From here, click the Configuration tab to visit the ASM Configuration page, where you can modify the ASM instance s parameters. You can also go to the ASM main page and check your instance s performance. Let s review the manual ASM startup and shutdown procedures.

The STARTUP command for an ASM instance is quite similar to the STARTUP command for regular Oracle databases, with a couple of interesting differences. During the mount phase of the normal Oracle STARTUP command, an Oracle database reads the control file and mounts the file systems specified there. An ASM instance doesn t have any file systems to mount and instead mounts the disk groups that you specify in the ASM_DISKGROUPS initialization parameter. The NOMOUNT command is similar to the regular Oracle NOMOUNT command: it starts an ASM instance, but doesn t mount any disk groups. Listing 17-8 shows how the STARTUP NOMOUNT and STARTUP MOUNT commands work in an ASM instance. Listing 17-8. The STARTUP NOMOUNT and STARTUP MOUNT Commands in an ASM Instance SQL> STARTUP NOMOUNT; ASM instance started Total System Global Area 79691776 bytes Fixed Size 1216820 bytes Variable Size 53309132 bytes ASM Cache 25165824 bytes SQL> SELECT name FROM v$database; select name from v$database * ERROR at line 1: ORA-01507: database not mounted SQL> ALTER DATABASE MOUNT; alter database mount * ERROR at line 1: ORA-15000: command disallowed by current instance type SQL> SQL> ALTER DATABASE OPEN; alter database open * ERROR at line 1: ORA-15000: command disallowed by current instance type SQL> To use ASM, you have to have a running ASM instance, and since there aren t any data files in an ASM instance, you can t use the STARTUP command s MOUNT or OPEN options. When you issue a STARTUP FORCE command, the ASM instance is first shut down with an internal STARTUP ABORT command and the instance is restarted. You can prevent any client Oracle database instances from connecting to the ASM instance by using the STARTUP RESTRICT command.