Asynchronous I/O Operations

enable_adio_debug

Parameter description: Specifies whether to enable logging related to ADIO, which helps to locate ADIO-related issues. General users are not advised to set this O&M parameter.

Type: SUSET

Value range: Boolean

• on or true indicates the log switch is enabled.
• off or false indicates the log switch is disabled.

Default value: off

enable_fast_allocate

Parameter description: Specifies whether the quick allocation switch of the disk space is enabled. This switch can be enabled only in the XFS file system.

Type: SUSET

Value range: Boolean

• on or true indicates that this function is enabled.
• off or false indicates that the function is disabled.

Default value: off

prefetch_quantity

Parameter description: Specifies the number of row-store prefetches using the ADIO.

Type: USERSET

Value range: an integer ranging from 1024 to 1048576. The unit is 8 KB.

Default value: 32 MB

backwrite_quantity

Parameter description: Specifies the number of row-store writes using the ADIO.

Type: USERSET

Value range: an integer ranging from 1024 to 1048576. The unit is 8 KB.

Default value: 8MB

cstore_prefetch_quantity

Parameter description: Specifies the number of column-store prefetches using the ADIO.

Type: USERSET

Value range: an integer. The value range is from 1024 to 1048576 and the unit is KB.

Default value: 32 MB

cstore_backwrite_quantity

Parameter description: Specifies the number of column-store writes using the ADIO.

Type: USERSET

Value range: an integer. The value range is from 1024 to 1048576 and the unit is KB.

Default value: 8MB

cstore_backwrite_max_threshold

Parameter description: Specifies the maximum number of column-store writes buffered in the database using the ADIO.

Type: USERSET

Value range: an integer ranging from 4096 to INT_MAX/2, in KB

Default value: 2 GB

fast_extend_file_size

Parameter description: Specifies the disk size that the row-store pre-scales using the ADIO.

Type: SUSET

Value range: an integer. The value range is from 1024 to 1048576 and the unit is KB.

Default value: 8MB

effective_io_concurrency

Parameter description: Specifies the number of requests that can be simultaneously processed by the disk subsystem. For the RAID array, the parameter value must be the number of disk drive spindles in the array.

Type: USERSET

Value range: an integer ranging from 0 to 1000

Default value: 1

cu_preload_max_distance

Parameter description: Specifies the maximum number of CU groups that can be prefetched. This is supported only by clusters of version 9.1.0.100 or later.

Type: USERSET

Value range: an integer ranging from 0 to 1024. The value 0 indicates that prefetching is disabled.

Default value: 20

cu_preload_count

Parameter description: Specifies the maximum number of CUs to be prefetched. This parameter is supported only by clusters of version 9.1.0 or later.

Type: USERSET

Value range: an integer. The value ranges from 0 to 10000. The value 0 indicates that prefetching is disabled.

Default value: 600