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Starting with Exadata software version 11.2.3.2, an under-performing disk can be detected and removed from an active configuration. This feature applies to both hard disks and flash disks. About stora...

The automatic disk management feature is about automating ASM disk operations in an Exadata environment. The automation functionality applies to both planned actions (for example, deactivating griddis...

This post is about the amount of space allocated to ASM based files. The smallest amount of space ASM allocates is an allocation unit (AU). The default AU size is 1 MB, except in Exadata where the def...

Oracle Database version 12c has been released, which means a brand new version of ASM is out! Notable new features are Flex ASM, proactive data validation and better handling of disk management operat...

Starting with version 12.1, ASM replicates the physically addressed metadata. This means that ASM maintains two copies of the disk header, the Free Space Table and the Allocation Table data. Note that...

The ASM Free Space Table (FST) provides a summary of which allocation table blocks have free space. It contains an array of bit patterns indexed by allocation table block number. The table is used to ...

Every ASM disk contains at least one Allocation Table (AT) that describes the contents of the disk. The AT has one entry for every allocation unit (AU) on the disk. If an AU is allocated, the Allocati...

The Partnership and Status Table (PST) contains the information about all ASM disks in a disk group – disk number, disk status, partner disk number, heartbeat info and the failgroup info (11g and late...

An ASM instance manages the metadata needed to make ASM files available to Oracle databases and other ASM clients. ASM metadata is stored in disk groups and organised in metadata structures. These met...

When diagnosing ASM issues, it helps to know a bit about the setup - disk group names and types, the state of disks, ASM instance initialisation parameters and if any rebalance operations are in progr...