ORACLEAUTOMATICSTORAGEMANAGEMENT-Chapter 2 ASMinstance (1)

Chapter 2 asm instanceasm instance type: After 10 Gb, an ASM type is added to the ORACLE instance type. Set the parameter INSTANCE_TYPE = ASM.
ASM instance startup command: startupNomountStart the instance and background process, but no disk group is mounted.MountLater, the instance starts the disk group specified by ASM_DISKGROUPS In the parameter file, and if the parameter is null, an ORA-15110 error message is triggered. ASM introduced for the mount command after 11GRestrictedStartup parameters: Start the specified disk group of ASM_DISKGROUPS in exclusive mode and restrict RDBMS access to the disk group. The restricted command is particularly useful when maintaining the disk group or rebalance. Note: resticted can mount a disk group at the disk level, rather than the instance level. The advantage is that it provides fine-grained restrictions. For example:

Alter diskgroup data mount restricted; select name, state from v $ asm_diskgroup; name state ---------------------- --------------------- DATA RESTRICTED

Background processes: the ASM background processes start with asm _, just as rdbms starts with ora. 11g asm background process Introduction

ARBxThese are the slave processes that do the rebalance activity (where x Is a number ). CKPTThe CKPTprocess manages cross-instance CALS (in RAC ). DBWRThis process manages the SGA buffer cache in the ASM instance. DBWRwrites out dirty buffers (changed metadata buffers) from the ASM Buffer cache to disk. GMONThis process is responsible for managing the disk-level activities (Drop/offline) and advancing diskgroup compatibility. KATEThe Konductor or ASM Temporary Errands (KATE) process is used To process disks online. This process runs in the ASM instance and is started Only when an offlined disk is onlined. LGWRThe LGWRprocess maintains the ASM Active Change Directory (ACD) buffers from the ASM instance and flushes ACD change records Disk. MARKThe Mark Allocation Unit (AU) for Resync Koordinator (MARK) Process coordinates the updates to the Staleness Registry when the disks go Offline. This process runs in the RDBMS instance and is started only when Disks go offline in ASM redundancy diskgroups. PINGThe PINGprocess measures network latency and has the same Functionality in RDBMS instances. PMONThis manages processes and process death in the ASM instance. PSP0This process spawner process is responsible for creating and Managing other Oracle processes. PZ9xThese processes are parallel slave processes (where xis a number ), Used in fetching data on behalf of GV $ queries. RBALThis opens all device files as part of discovery and coordinates Rebalance activity. SMONThis process is the system monitor and also acts as a liaison to Cluster Synchronization Services (CSS) process (in Oracle Clusterware) Node monitoring. VKTMThis process is used to maintain the fast timer and has the same Functionality in the RDBMS instances.

Asm sga and parameter settings require only a few parameters to start ASM. The parameter file can be pfile or spfile.

*. Instance_type = asm *. Asm_diskgroups = DATA, FLASH *. Processses = 100 * *** Note that asm_diskstring is site-specific and platform specific *. Asm_diskstring = '/dev/rdsk/c3t19d * s4' -- Note that if you manually add the asm disk group and forget to update this parameter, the missing disk group cannot be automatically taken after restart. *. Remote_login_passwordfile = 'shared' ****** ** For 11g use only the diagnostics directory. *. Diagnostic_dest = '/opt/app/admin/+ ASM/diag' -- The diagnostic_dest of 11g replaces the bdump, cdump, and udump of 10g. ******* ** For 10g use the standard dump locations *. Background_dump_dest = '/opt/app/admin/+ ASM/bdump' *. Core_dump_dest = '/opt/app/admin/+ ASM/cdump' *. User_dump_dest = '/opt/app/admin/+ ASM/udump' *******

The three parameters BACKGROUND_DUMP_DEST, CORE_DUMP_DEST, and USER_DUMP_DEST have been deprecated in 11G. do not configure these three parameters in the ASM instance. If diagnostic_dest is not configured, the default location is $ ORACLE_BASE/diag. For example, the following directory structure is created: $ ORACLE_BASE/diag/<INSTANCE type>/<DB_UNIQUE_NAME>/<ORACLE_SID>

SQL> SELECT NAME, VALUE FROM V $ DIAG_INFO NAME VALUE ------------------------- Diag Enabled TRUE ADR Base/u01/app/oracle ADR Home/u01/app/oracle/diag/asm/+ ASM1 Diag Trace/u01/app/oracle/diag/asm/+ ASM1/trace Diag Alert/u01/app/oracle/diag/asm/+ ASM1/alert Diag Incident/u01/app/oracle/diag/asm/+ ASM1/incident Diag Cdump/u01/app/oracle/diag/asm/+ ASM1/cdump Health Monitor/u01/app/oracle/diag/asm/+ ASM1/hm Default Trace File

All diagnostic information in 11g can be managed using adrci.
Best practices ASM Parameters

In 11g, ASM can use the AMM feature to configure MEMORY_TARGET and MEMORY_MAX_TARGET in init. ora. Like rdbms, these two parameters can achieve automatic memory management. However, since the asm memory usage is very stable, ORACLE best practice is not to set these two parameters. By default, 256 M is used. This configuration conforms to most environments. Note: In the production environment, the use of default parameters by ASM may cause an 4031 error at the ASM instance level. According to the MOS documentation, we recommend that the memory be allocated at least 1 GB, which is in conflict with the best practice, It can be seen that the best practices of ORACLE are not necessarily reliable, but can be used as a reference.

If you need to manually adjust the memory, you only need to modify MEMORY_TARGET to change alter system set memeory_target = 300 M;
Of course, if you want to disable AMM, you can set MEMROY_target to 0, but the shared_pool, large_pool, and db_cache_size parameters need to be configured.

DB_CACHE_SIZEThis value determines the size of the buffer cache, which Is used to cache ASM metadata blocks. The DB_CACHE_SIZEis based on A metadata block size of 4 K. This block size is the buffer page size of Cached metadata and has no bearing or impact on the database block size. Db_cache_size is used to cache metadata blocks. It is based on metadata block size and 4 K, It is not affected by db block size. SHARED_POOLThis is used for standard memory usage (control structures And so on) to manage the instance. The value is also used to store open file Extent maps. Shared_pool is used to store data structures used for instance management. Extent maps. LARGE_POOLThe LARGE_POOLvalue is used for large page allocations. PROCESSESThis ASM init. ora parameter limits the number of processes That can start in ASM instance. You may need to modify this parameter from Its default setting for Oracle Database 10 gASM instances. The following Recommendation pertains to Oracle Database 10.1.0.3 through 10.2.xand Will work for RAC and non-RAC systems: Processes = 25 + (10 +[Max number of concurrent database file Creations, and file extend operations possible]) * N The PROCESSES configuration can be calculated based on the above formula. Formula description: WhereNIs the number of RDBMS instance (ASM clients) connecting to ASM TheSource of concurrent file creationsCan be any of the following: Several concurrent CREATE TABLESPACEcommands Creation of a partitioned table with several tablespace creations RMAN backup channels Concurrent archive log file creations Max number of concurrent database file creations:It can be the number of concurrent tasks in create tablespace, the number of tablespaces involved in creating partition tables, the number of channels allocated by rman backup, and the number of concurrent archive Creation

In 10 Gb, ASM does not have the AMM feature. The general configuration is as follows:

SHARED_POOL_SIZE: 128 MB LARGE_POOL: 12 MB DB_CACHE_SIZE: 64 MB

We can use SQLPLUS to manage ASM like databases, such as SQL> SHOW SGA. However, note that most rdbms parameters are not applicable to ASM instances, for example, controlfile_files when you try to set this parameter, you will receive an error ORA-15021: parameter "control_files" is not valid in asm instance
Note: PARAMETER file parameters: SQL> SHOW PARAMETER CONTROL
NAME TYPE VALUE
------------------------------ -------------------------------------- Control_files string/opt/oracle/app/product/10gr2/
Dbs/cntrl + ASM. dbf
However, you cannot find this parameter in the operating system. The internal default value of this parameter has no practical significance for ASM.
Two files stored in $ ORACLE_HOME/dbs: AB _ <ASM SID>. the dat file is generated when the asm strength is started, and the database instance obtains the environment information when connecting to the ASM instance. If the file is deleted, RDBMS cannot communicate with the ASM instance.
Hc _ <SID>. dat EM uses this file to monitor and check instances. If this file is removed, the health check results will be incorrect.
The ASM. dat file does not affect the performance of ASM. The file stores only the connection information and communicates with the ASM instance when necessary. Note: you may need to set implicit parameters to assist in problem diagnosis, for example, diagnosis parameter _ disable_instance_parms_check (this parameter does not need to be 11 GB)