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DISK_CACHE_INFORMATION structure (winioctl.h)

  • Article

Provides information about the disk cache.This structure is used by the IOCTL_DISK_GET_CACHE_INFORMATION and IOCTL_DISK_SET_CACHE_INFORMATION control codes.

Syntax

typedef struct _DISK_CACHE_INFORMATION {
  BOOLEAN                       ParametersSavable;
  BOOLEAN                       ReadCacheEnabled;
  BOOLEAN                       WriteCacheEnabled;
  DISK_CACHE_RETENTION_PRIORITY ReadRetentionPriority;
  DISK_CACHE_RETENTION_PRIORITY WriteRetentionPriority;
  WORD                          DisablePrefetchTransferLength;
  BOOLEAN                       PrefetchScalar;
  union {
    struct {
      WORD Minimum;
      WORD Maximum;
      WORD MaximumBlocks;
    } ScalarPrefetch;
    struct {
      WORD Minimum;
      WORD Maximum;
    } BlockPrefetch;
  } DUMMYUNIONNAME;
} DISK_CACHE_INFORMATION, *PDISK_CACHE_INFORMATION;

Members

ParametersSavable

Indicates whether the device is capable of saving any parameters in nonvolatile storage.

ReadCacheEnabled

Indicates whether the read cache is enabled.

WriteCacheEnabled

Indicates whether the write cache is enabled.

ReadRetentionPriority

Determines the likelihood of data cached from a read operation remaining in the cache. This data might be given a different priority than data cached under other circumstances, such as from a prefetch operation.

This member can be one of the following values from the DISK_CACHE_RETENTION_PRIORITY enumeration type.

Value Meaning
EqualPriority
0
 No data is held in the cache on a preferential basis.
KeepPrefetchedData
1
 A preference is to be given to prefetched data.
KeepReadData
2
 A preference is to be given to data cached from a read operation.

WriteRetentionPriority

Determines the likelihood of data cached from a write operation remaining in the cache. This data might be given a different priority than data cached under other circumstances, such as from a prefetch operation.

DisablePrefetchTransferLength

Disables prefetching. Prefetching might be disabled whenever the number of blocks requested exceeds the value in DisablePrefetchTransferLength. When zero, prefetching is disabled no matter what the size of the block request.

PrefetchScalar

If this member is TRUE, the union is a ScalarPrefetch structure. Otherwise, the union is a BlockPrefetch structure.

DUMMYUNIONNAME

DUMMYUNIONNAME.ScalarPrefetch

DUMMYUNIONNAME.ScalarPrefetch.Minimum

The scalar multiplier of the transfer length of the request. This member is valid only when PrefetchScalar is TRUE. When PrefetchScalar is TRUE, this value is multiplied by the transfer length to obtain the minimum amount of data that can be prefetched into the cache on a disk operation.

DUMMYUNIONNAME.ScalarPrefetch.Maximum

The scalar multiplier of the transfer length of the request. This member is valid only when PrefetchScalar is TRUE. When PrefetchScalar is TRUE, this value is multiplied by the transfer length to obtain the maximum amount of data that can be prefetched into the cache on a disk operation.

DUMMYUNIONNAME.ScalarPrefetch.MaximumBlocks

The maximum number of blocks which can be prefetched.

DUMMYUNIONNAME.BlockPrefetch

DUMMYUNIONNAME.BlockPrefetch.Minimum

The minimum amount of data that can be prefetched into the cache on a disk operation, as an absolute number of disk blocks. This member is valid only when PrefetchScalar is FALSE.

DUMMYUNIONNAME.BlockPrefetch.Maximum

The maximum amount of data that can be prefetched into the cache on a disk operation, as an absolute number of disk blocks. This member is valid only when PrefetchScalar is FALSE.

Requirements

Requirement Value
Minimum supported client Windows XP [desktop apps only]
Minimum supported server Windows Server 2003 [desktop apps only]
Header winioctl.h (include Windows.h)

See also

IOCTL_DISK_GET_CACHE_INFORMATION

IOCTL_DISK_SET_CACHE_INFORMATION