lvm_queryvg Subroutine

Base Operating System and Extensions Technical Reference, Volume 1

lvm_queryvg Subroutine

Purpose

Queries a volume group and returns pertinent information.

Library

Logical Volume Manager Library (liblvm.a)

Syntax

#include <lvm.h>

int lvm_queryvg (VG_ID, QueryVG, PVName)
struct unique_id *VG_ID;
struct queryvg **QueryVG;
char *PVName;

Description

Note: You must have root user authority to use this subroutine.

The lvm_queryvg subroutine returns information on the volume group specified by the VG_ID parameter.

The queryvg structure , found in the lvm.h file, contains the following fields:

struct queryvg {
      long maxlvs;
      long ppsize;
      long freespace;
      long num_lvs;
      long num_pvs;
      long total_vgdas;  
      struct lv_array *lvs;
      struct pv_array *pvs;  
 }
 struct pv_array {  
     struct unique_id pv_id;
     long pvnum_vgdas;  
     char   state;
     char   res[3];
 }
 struct lv_array {
      struct lv_id   lv_id;
      char  lvname[LVM_NAMESIZ];
      char   state;
      char   res[3]; 
 }

Field	Description
`maxlvs`	Specifies the maximum number of logical volumes allowed in the volume group.
`ppsize`	Specifies the size of all physical partitions in the volume group. The size in bytes of each physical partitions is 2 to the power of the `ppsize` field.
`freespace`	Contains the number of free physical partitions in this volume group.
`num_lvs`	Indicates the number of logical volumes.
`num_pvs`	Indicates the number of physical volumes.
`total_vgdas`	Specifies the total number of volume group descriptor areas for the entire volume group.
`lvs`	Points to an array of unique IDs, names, and states of the logical volumes in the volume group.
`pvs`	Points to an array of unique IDs, states, and the number of volume group descriptor areas for each of the physical volumes in the volume group.

The PVName parameter enables the user to query from a descriptor area on a specific physical volume instead of from the Logical Volume Manager's (LVM) most recent, in-memory copy of the descriptor area. This method should only be used if the volume group is varied off. The data returned is not guaranteed to be most recent or correct, and it can reflect a back level descriptor area. The Pvname parameter should specify either the full path name of the physical volume that contains the descriptor area to query or a single file name that must reside in the /dev directory (for example, rhdisk1). The name must represent a raw device. If a raw or character device is not specified for the PVName parameter, the Logical Volume Manager will add an r to the file name in order to have a raw device name. If there is no raw device entry for this name, the LVM returns the LVM_NOTCHARDEV error code. This field must be a null-terminated string of from 1 to LVM_NAMESIZ bytes, including the null byte. If a PVName is specified, the LVM will return the VG_ID to the user through the VG_ID pointer passed in. If the user wishes to query from the LVM in-memory copy, the PVName parameter should be set to null. When using this method of query, the volume group must be varied on, or an error will be returned.

Note: As long as the PVName parameter is not null, the LVM will attempt a query from a physical volume and not its in-memory copy of data.

In addition to the PVName parameter, the caller passes the unique ID of the volume group to be queried (VG_ID) and the address of a pointer to a queryvg structure. The LVM will separately allocate enough space for the queryvg structure, as well as the lv_array and pv_array structures, and return the address of the completed structure in the QueryVG parameter passed in by the user. The user is responsible for freeing the space by freeing the lv and pv pointers and then freeing the QueryVG pointer.

Parameters

VG_ID	Points to a unique_id structure that specifies the volume group to be queried.
QueryVG	Specifies the address of a pointer to the queryvg structure.
PVName	Specifies the name of the physical volume that contains the descriptor area to query and must be the name of a raw device.

Return Values

The lvm_queryvgn subroutine returns a value of 0 upon successful completion.

Error Codes

If the lvm_queryvg subroutine fails it returns one of the following error codes:

LVM_ALLOCERR	The subroutine cannot allocate enough space for a complete buffer.
LVM_FORCEOFF	The volume group has been forcefully varied off due to a loss of quorum.
LVM_INVALID_PARAM	An invalid parameter was passed into the routine.
LVM_OFFLINE	The volume group is offline and should be online.

If the query originates from the varied-on volume group's current volume group descriptor area, one of the following error codes may be returned:

LVM_DALVOPN	The volume group reserved logical volume could not be opened.
LVM_INV_DEVENT	The device entry for the physical volume specified by the PVName parameter is invalid and cannot be checked to determine if it is raw.
LVM_MAPFBSY	The volume group is currently locked because system management on the volume group is being done by another process.
LVM_MAPFOPN	The mapped file, which contains a copy of the volume group descriptor area used for making changes to the volume group, could not be opened.
LVM_MAPFRDWR	Either the mapped file could not be read, or it could not be written.
LVM_NOTCHARDEV	A device is not a raw or character device.

If a physical volume name has been passed, requesting that the query originate from a specific physical volume, one of the following error codes may be returned:

LVM_BADBBDIR	The bad-block directory could not be read or written.
LVM_LVMRECERR	The LVM record, which contains information about the volume group descriptor area, could not be read.
LVM_NOPVVGDA	There are no volume group descriptor areas on this physical volume.
LVM_NOTVGMEM	The physical volume is not a member of a volume group.
LVM_PVDAREAD	An error occurred while trying to read the volume group descriptor area from the specified physical volume.
LVM_PVOPNERR	The physical volume device could not be opened.
LVM_VGDA_BB	A bad block was found in the volume group descriptor area located on the physical volume that was specified for the query. Therefore, a query cannot be done from this physical volume.

Implementation Specifics

This subroutine is part of Base Operating System (BOS) Runtime.

Related Information

The lvm_varyonvg subroutine.

List of Logical Volume Subroutines and Logical Volume Programming Overview in AIX Version 4.3 General Programming Concepts: Writing and Debugging Programs.