IBM General Parallel File System for AIX: Administration and Programming Reference

gpfsAccessRange_t Structure

Name

gpfsAccessRange_t - Declares an access range within a file for an application.

Structure

typedef struct
{
  int          structLen;
  int          structType;
  offset_t     start;
  offset_t     length;
  int          isWrite;
  char         padding[4];
} gpfsAccessRange_t; 

Description

The application will access file offsets within the given range, and will not access offsets outside the range. Violating this hint may produce worse performance than if no hint was specified.

This hint is useful in situations where a file is partitioned coarsely among several nodes. If the ranges do not overlap, each node can specify which range of the file it will access, with a performance improvement in some cases, such as for sequential writing within a range.

Subsequent GPFS_ACCESS_RANGE hints will replace a hint passed earlier.

Members

structLen

Length of the gpfsAccessRange_t structure.

structType

The hint identifier GPFS_ACCESS_RANGE.

start

The start of the access range offset, in bytes, from beginning of file.

length

Length of the access range.

0 indicates to end of file.

isWrite

0 indicates read access.

1 indicates write access.

padding[4]

Provided to ensure the length of the gpfsAccessRange_t structure is a multiple of 8 bytes in length. There is no need to initialize this field.