Asynchronous I/O Operations

enable_adio_debug

Parameter description: Specifies whether O&M personnel are allowed to generate some ADIO logs to locate ADIO issues. This parameter is used only by developers. Common users are advised not to use it.

This parameter is a SUSET parameter. Set it based on instructions provided in Table 1 GUC parameters.

Value range: Boolean

• on or true indicates that generation of ADIO logs is allowed.
• off or false indicates that generation of ADIO logs is disallowed.

Default value: off

enable_adio_function

Parameter description: Specifies whether to enable the ADIO function.

The current version does not support enabling the asynchronous IO function. By default, this function is disabled. Please do not modify it yourself.

Value range: Boolean

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

Default value: off

enable_fast_allocate

Parameter description: Specifies whether the quick disk space allocation is enabled.

This parameter is a SUSET parameter. Set it based on instructions provided in Table 1 GUC parameters. This function can be enabled only in the XFS file system.

Value range: Boolean

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

Default value: off

prefetch_quantity

Parameter description: Specifies the amount of the I/O that the row-store prefetches using the ADIO.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1 GUC parameters.

Value range: an integer ranging from 128 to 131072. The unit is 8 KB.

Default value: 32MB (4096 x 8 KB)

backwrite_quantity

Parameter description: Specifies the amount of I/O that the row-store writes using the ADIO.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1 GUC parameters.

Value range: an integer ranging from 128 to 131072. The unit is 8 KB.

Default value: 8MB (1024 x 8 KB)

cstore_prefetch_quantity

Parameter description: Specifies the amount of I/O that the column-store prefetches using the ADIO.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1 GUC parameters.

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

Default value: 32MB

cstore_backwrite_quantity

Parameter description: Specifies the amount of I/O that the column-store writes using the ADIO.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1 GUC parameters.

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

Default value: 8MB

cstore_backwrite_max_threshold

Parameter description: Specifies the maximum amount of buffer I/O that the column-store writes in the database using the ADIO.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1 GUC parameters.

Value range: an integer ranging from 4096 to INT_MAX/2. The unit is KB.

Default value: 2GB

fast_extend_file_size

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

This parameter is a SUSET parameter. Set it based on instructions provided in Table 1 GUC parameters.

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

Default value: 8MB

effective_io_concurrency

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

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1 GUC parameters.

Value range: an integer ranging from 0 to 1000

Default value: 1