ORACLE AUTOMATIC STORAGE Management Translator-Chapter II (1)

Chapter II ASM INSTANCEASM Instance Type:After 10g, the Oracle instance type adds an ASM type, and the parameter instance_type=asm is set.
ASM Instance startup command: Startup  NomountLaunching instances and background processes, but not mounting disk groups MountLater, the instance launches the specified disk group in the asm_diskgroups parameter file, and if the parameter is empty, the ORA-15110 error message is triggered. ASM 11G later introduced the Mount command to the restrictedStartup parameters, which are exclusive to start asm_diskgroups specified disk groups, restrict RDBMS access to disk groups, and restricted commands are particularly useful when maintaining disk groups or rebalance. Note: resticted can mount disk groups at the disk group level instead of the instance level, with the benefit of providing fine-grained restrictions. Such as:

Alter DiskGroup data Mount Restricted;select name,state from V$asm_diskgroup;name State----- ------------------------------------DATA RESTRICTED

Background processes: ASM background processes start with asm_, just as the RDBMS begins with Ora_. 11g ASM Background Process Introduction

ARBX These is the slave processes that does the rebalance activity (where x is a number). Ckptthe Ckptprocess manages Cross-instance calls (in RAC). DBWR This process manages the SGA buffer cache in the ASM instance. DBW Rwrites out dirty buffers (changed metadata buffers) from the ASM Buffer cache to disk. Gmon This process was responsible for managing the disk-level activities (Drop/offline) and advancing diskgroup compatibility. KATE The Konductor or ASM temporary errands (KATE) process is used To process disks online. This process runs in the ASM instance and is started A offlined disk is onlined. LGWRThe lgwrprocess maintains the ASM Active change Directory (ACD) buffers from the ASM instance and flushes ACD change records to Disk. MARK The 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 was started only when Disks go offline in ASM redundancy diskgroups. PINGThe pingprocess measures network latency and has the same Functionality in RDBMS instances. Pmon This manages processes and process death in the ASM instance. PSP0 This process Spawner process was responsible for creating and Managing other Oracle processes. pz9x These processes is parallel slave processes (where XIs a number), Used in fetching data on behalf of Gv$queries. Rbal This opens all device files as part of discovery and coordinates the Rebalance activity. Smon This process is the System Monitor and also acts as a liaison to the Cluster synchronization Services (CSS) process (in Oracle clusterware) for Node monitoring. Vktm This are used to maintain the fast timer and have the same Functionality in the RDBMS instances.

ASM SGA and parameter setup ASM boot requires very few parameters, parameter file can be pfile or spfile

*.instance_type=asm *.asm_diskgroups=data,flash *.processes=100 Note that asm_diskstring is site-specific and platform specific *.asm_diskstring= '/DEV/RDSK/C3T19D*S4 '--Note If you manually add ASM disk groups forget to update this parameter or the missing disk group will not be automatically brought up after reboot *.remote_login_passwordfile= ' SHARED ' ****** **for 11g use is only the diagnostics directory. The diagnostic_dest of *.diagnostic_dest= '/opt/app/admin/+asm/diag '--11g replaced the bdump,cdump,udump of 10g, apparently with a lot of introductions. ******* **for 10g use of 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 ' *******

Background_dump_dest,core_dump_dest, and user_dump_dest These three parameters have been deprecated in 11g, the ASM instance does not configure these three parameters. If Diagnostic_dest is not configured, the default location for $oracle_base/diag such as 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/+ASM/+ASM1 Diag Trace/u01/app/oracle/diag/asm/+asm/+asm1/trace Diag Alert/u01/app/oracle/diag/asm/+asm/+asm1/alert Diag incident/u01/app/oracle/diag/asm/+asm/+asm1/incident Diag Cdump/u01/app/oracle/diag/asm/+asm/+asm1/cdump Health MONITOR/U01/APP/ORACLE/DIAG/ASM/+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, and the same parameters as the RDBMS enable automatic memory management. However, because ASM memory usage is very smooth, Oracle best practice is to not set these two parameters, using 256M by default, this configuration conforms to most environments. Note: ASM using default parameters in a production environment may raise 4031 errors at the ASM instance level, which is inconsistent with best practices, as it is recommended to allocate at least 1G of memory according to the MoS document. Oracle's best practices are not necessarily reliable, but can be used as a reference.

If there is a need to manually adjust the memory, only need to modify Memory_target can be alter system set memeory_target=300m;
Of course if you want to disable AMM you can set the Memroy_target to 0, but the shared_pool,large_pool,db_cache_size three parameters need to be configured.

db_cache_size This 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 4K. This block size is the buffer page size of the Cached metadata and have no bearing or impact on the database block size. Db_cache_size is used to cache metadata block, which is based on metadata block size and 4K, Not affected by the DB block size. Shared_pool This was used for the 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 the data structure of the management instance, if the control structure is also stored Extent maps and so on. Large_poolThe large_poolvalue is used for LARGE page allocations. PROCESSES This ASM Init.ora parameter limits the number of processes That can-start in ASM instance. Need to modify this parameter from Its default setting for Oracle Database 10gASM instances. The following Recommendation pertains to Oracle Database 10.1.0.3 through 10.2.xand Would 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 formula above. Formula Description: where N Is the number of the RDBMS instance (ASM clients) connecting to ASM The source of concurrent file Creations Can is 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:Can be create tablespace concurrency number, the number of table spaces involved in creating partition table, Rman Backup allocated channels, concurrent creation of archives

In 10g, ASM has no amm characteristics, and is typically configured as follows:

Shared_pool_size:128mb Large_pool:12mb Db_cache_size:64mb

We can use Sqlplus to manage ASM like a database, such as: Sql>show SGA but note that most RDBMS parameters do not work with ASM instances, such as Controlfile_ Files receive an error when you try to set this parameter 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
But in the operating system you can not find this parameter, this parameter when the internal default value for ASM is no practical significance
Two files stored under $oracle_home/dbs: ab_<asm sid>.dat This file is generated at ASM Power startup, while the DB instance is connected to an ASM instance to obtain the environment information, If the file is deleted, the RDBMS will not be able to communicate with the ASM instance.
Hc_<sid>.dat EM uses this file for monitoring and monitoring of instances. If the file is removed, the health check results are wrong.
asm. dat files do not have a performance impact on ASM, and the files contain only connection information and are required to communicate with ASM instances. Note that sometimes it may be necessary to set the implied parameters to assist in diagnosing the problem, such as: Diagnostic parameter _disable_instance_parms_check (this parameter does not need 11g)