Given that the new and old storage are both visible to ASM, simply add the new disks to the ASM disk group and drop the old disks. ASM rebalance will migrate data online.
GRD stands for Global Resource Directory. The GES and GCS maintain records of the status of each datafile and each cached block using global resource directory. This process is referred to as cache fusion and helps in data integrity.
Not applicable! ASM has no files to backup, as its does not contain controlfile,redo logs etc.
RMAN is the recommended and most complete and flexible method to backup and trport database files in ASM.
ASMCMD copy is good for copying single files
• Supports all Oracle file types
• Can be used to instantiate a Data Guard environment
• Does not update the controlfile
• Does not create OMF files
Oracle Clusterware is used to manage high-availability operations in a cluster. Anything that Oracle Clusterware manages is known as a CRS resource. Some examples of CRS resources are database, an instance, a service, a listener, a VIP address, an application process etc.
ASM provides filesystem and volume manager capabilities built into the Oracle database kernel. Withthis capability, ASM simplifies storage management tasks, such as creating/laying out databases and disk space management. Since ASM allows disk management to be done using familiar create/alter/drop SQL statements, DBAs do not need to learn a new skill set or make crucial decisions on provisioning.
The following are some key benefits of ASM:
The Clusterware is installed on each node (on an Oracle Home) and on the shared disks (the voting disks and the CSR file).
There are two types of connection load-balancing: server-side load balancing and client-side load balancing.
A disk group consists of multiple disks and is the fundamental object that ASM manages. Each disk group contains the metadata that is required for the management of space in the disk group. The ASM instance manages the metadata about the files in a Disk Group in the same way that a file system manages metadata about its files. However, the vast majority of I/O operations do not pass through the ASM instance. In a moment we will look at how file I/O works with respect to the ASM instance.
Oracle Clusterware manages CRS resources based on the configuration information of CRS resources stored in OCR (Oracle Cluster Registry).
ASM can use variable size data extents to support larger files, reduce memory requirements, and improve performance.
Each data extent resides on an individual disk.
Data extents consist of one or more allocation units.
The data extent size is:
ASM stripes files using extents with a coarse method for load balancing or a fine method to reduce latency.
No. The RDBMS does I/O directly to the raw disk devices, the FILESYSTEMIO_OPTIONS parameter is only for filesystems.
In Oracle Database 10g/11g there are two types of instances: database and ASM instances. The ASM instance, which is generally named +ASM, is started with the INSTANCE_TYPE=ASM init.ora parameter. This parameter, when set, signals the Oracle initialization routine to start an ASM instance and not a standard database instance. Unlike the standard database instance, the ASM instance contains no physical files; such as logfiles, controlfiles or datafiles, and only requires a few init.ora parameters for startup.
Upon startup, an ASM instance will spawn all the basic background processes, plus some new ones that are specific to the operation of ASM. The STARTUP clauses for ASM instances are similar to those for database instances. For example, RESTRICT prevents database instances from connecting to this ASM instance. NOMOUNT starts up an ASM instance without mounting any disk group. MOUNT option simply mounts all defined diskgroups
For RAC configurations, the ASM SID is +ASMx instance, where x represents the instance number.
ASM imposes the following limits:
Yes. ASM can be at a higher version or at lower version than its client databases. There’s two:
components of compatiblity: Software compatibility
Diskgroup compatibility attributes: compatible.asm, compatible.rdbms.
We have v$ views that are instance specific. In addition we have GV$ views called as global views that has an INST_ID column of numeric data type.GV$ views obtain information from individual V$ views.
It is recommended to run the listener from the ASM HOME. This is particularly important for RAC env, since the listener is a node-level resource. In this config, you can create additional [user] listeners from the database homes as needed.
Rebalance time is heavily driven by the three items:
1) Amount of data currently in the diskgroup
2) IO bandwidth available on the server
3) ASM_POWER_LIMIT or Rebalance Power Level
HP Tru64 Unix, Veritas, Microsoft
A cluster File System (CFS) is a file system that may be accessed (read and write) by all members in a cluster at the same time. This implies that all members of a cluster have the same view.
The use of Bigfile tablespaces has no bearing on ASM (or vice versa). In fact most database object related decisions are trparent to ASM.
Oracle Clusterware manages CRS resources based on the configuration information of CRS resources stored in OCR (Oracle Cluster Registry).
The default parameter settings work perfectly for ASM. The only parameters needed for 11g ASM:
The database communicates with ASM instance using the ASMB (umblicus process) process. Once the database obtains the necessary extents from extent map, all database IO going forward is processed through by the database processes, bypassing ASM. Thus we say ASM is not really in the IO path. So, the question how do we make ASM go faster…..you don’t have to.
Oracle recommends two diskgroups to provide a balance of manageability, utilization, and performance.
We need to stop and delete the instance in the node first in interactive or silent mode. After that ASM can be removed using srvctl tool as follows:
No. Cross-platform disk group migration not supported. To move datafiles between endian-ness platforms, you need to use XTTS, Datapump or Streams.
It works great! Multipathing software is at a layer lower than ASM, and thus is trparent.
You may need to adjust ASM_DISKSTRING to specify only the path to the multipathing pseudo devices.
The OCFS2 is the Oracle (version 2) Cluster File System which can be used for the Oracle Real Application Cluster.
There is no best size! In most cases the storage team will dictate to you based on their standardized LUN size. The ASM administrator merely has to communicate the ASM Best Practices and application characteristics to storage folks :
• Need equally sized / performance LUNs
• Minimum of 4 LUNs
• The capacity requirement
• The workload characteristic (random r/w, sequential r/w) & any response time SLA
Using this info , and their standards, the storage folks should build a nice LUN group set for you.
The base software is installed on each node of the cluster and the database storage on the shared disks.
For clarification
• Separate Oracle Home for ASM and RDBMS.
• RDBMS instance connects to ASM using OSDBA group of the ASM instance.
Thus, software owner for each RDBMS instance connecting to ASM must be a member of ASM's OSDBA group.
• Choose a different OSDBA group for ASM instance (asmdba) than for RDBMS instance (dba)
• In 11g, ASM administrator has to be member of a separate SYSASM group to separate ASM Admin and DBAs.
ASM is not in the I/O path so ASM does not impede the database file access. Since the RDBMS instance is performing raw I/O, the I/O is as fast as possible.
Single Client Access Name (SCAN) is s a new Oracle Real Application Clusters (RAC) 11g Release 2 feature that provides a single name for clients to access an Oracle Database running in a cluster. The benefit is clients using SCAN do not need to change if you add or remove nodes in the cluster.