Asynchronous I/O Operations

enable_adio_debug

Parameter description: Specifies whether OM 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 function is no longer supported in the current version due to specification changes. Do not use this function.

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

Value range: Boolean

• on or true indicates that generation of logs is allowed.
• off or false indicates that generation of logs is not allowed.

Default value: off

This parameter cannot be enabled on in the current version. Even if it is manually enabled, the system automatically disables it.

enable_adio_function

Parameter description: Specifies whether to enable the ADIO function. This function is no longer supported in the current version due to specification changes. Do not use this function.

The current version does not support the asynchronous I/O function. This function is disabled by default. Do not modify the setting.

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 function is no longer supported in the current version due to specification changes. Do not use this function.

This parameter is a SUSET parameter. Set it based on instructions provided in Table 1. 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 function is no longer supported in the current version due to specification changes. Do not use this function.

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

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

Default value: 32 MB (4096 x 8 KB)

backwrite_quantity

Parameter description: Specifies the amount of I/O that the row-store writes using the ADIO. This function is no longer supported in the current version due to specification changes. Do not use this function.

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

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

Default value: 8 MB (1024 x 8 KB)

cstore_prefetch_quantity

Parameter description: Specifies the amount of I/O that the column-store prefetches using the ADIO. This function is no longer supported in the current version due to specification changes. Do not use this function.

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

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

Default value: 32 MB

cstore_backwrite_quantity

Parameter description: Specifies the amount of I/O that the column-store writes using the ADIO. This function is no longer supported in the current version due to specification changes. Do not use this function.

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

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 function is no longer supported in the current version due to specification changes. Do not use this function.

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

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

Default value: 2 GB

fast_extend_file_size

Parameter description: Specifies the disk size that the row-store pre-scales using the ADIO. This function is no longer supported in the current version due to specification changes. Do not use this function.

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

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 function is no longer supported in the current version due to specification changes. Do not use this function.

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

Value range: an integer ranging from 0 to 1000

Default value: 1

checkpoint_flush_after

Parameter description: Specifies the threshold for the number of pages flushed by the checkpointer thread. If the threshold is exceeded, the operating system is instructed to flush the pages cached in the operating system asynchronously. In GaussDB, the disk page size is 8 KB.

This parameter is a SIGHUP parameter. Set it based on instructions provided in Table 1.

Value range: an integer ranging from 0 to 256. 0 indicates that the asynchronous flush function is disabled. For example, if the value is 32, the checkpointer thread continuously writes 32 disk pages (that is, 32 x 8 = 256 KB) before asynchronous flush.

Default value: 256 KB

bgwriter_flush_after

Parameter description: Specifies the threshold for the number of pages flushed by the background writer thread. If the threshold is exceeded, the background writer thread instructs the operating system to asynchronously flush the pages cached in the operating system to disks. In GaussDB, the disk page size is 8 KB.

This parameter is a SIGHUP parameter. Set it based on instructions provided in Table 1.

Value range: an integer ranging from 0 to 256. 0 indicates that the asynchronous flush function is disabled. The size of a single page is 8 KB. For example, if the value is 64, the background writer thread continuously writes 64 disk pages (that is, 64 x 8 = 512 KB) before asynchronous flush.

Default value: 512 KB (64 pages)

backend_flush_after

Parameter description: Specifies the threshold for the number of pages flushed by the background writer thread. If the number of pages exceeds the threshold, the background writer thread instructs the operating system to asynchronously flush the pages cached in the operating system to disks. In GaussDB, the disk page size is 8 KB.

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

Value range: an integer ranging from 0 to 256. 0 indicates that the asynchronous flush function is disabled. The size of a single page is 8 KB. For example, if the value is 64, the backend thread continuously writes 64 disk pages (that is, 64 x 8 = 512 KB) before asynchronous flush.

Default value: 0