I've encountered many DBAs who hesitate to perform index maintenance due to unfounded fears of data loss. While the concern comes from a good place (protecting critical data), it's technically misguided. Let me explain why rebuilding indexes is fundamentally safe:

• Index rebuilds are metadata operations - they don't directly modify table data
• The operation creates new structures before dropping old ones (atomicity)
• SQL Server uses write-ahead logging for all DDL operations

Here's the actual sequence when rebuilding an index:

-- What happens under the hood during ONLINE rebuild
1. Creates new index structure in parallel
2. Applies all pending changes via log records
3. Swaps the new and old index pointers (metadata change)
4. Drops the old structure

For critical systems like Great Plains Dynamics, you can add extra protection:

-- Safe rebuild command for production
ALTER INDEX [IX_YourIndex] ON [dbo].[YourTable] 
REBUILD WITH (ONLINE = ON, MAXDOP = 4, SORT_IN_TEMPDB = ON);

For extremely cautious DBAs, implement this phased approach:

-- Phase 1: Test in isolation
DBCC CHECKTABLE('dbo.YourTable') WITH NO_INFOMSGS;
EXEC sp_helpindex 'dbo.YourTable';

-- Phase 2: Reorganize first (less intrusive)
ALTER INDEX ALL ON [dbo].[YourTable] REORGANIZE;

-- Phase 3: Sample rebuild on non-critical index
ALTER INDEX [IX_NonCritical] ON [dbo].[YourTable] 
REBUILD WITH (ONLINE = OFF, STATISTICS_NORECOMPUTE = ON);

-- Phase 4: Full production rollout during maintenance window

After any index operation, run these validation checks:

-- Verify index integrity
DBCC CHECKDB('YourDatabase') WITH NO_INFOMSGS;

-- Check fragmentation levels post-rebuild
SELECT 
    OBJECT_NAME(i.object_id) AS TableName,
    i.name AS IndexName,
    ips.avg_fragmentation_in_percent
FROM 
    sys.dm_db_index_physical_stats(DB_ID(), NULL, NULL, NULL, 'LIMITED') ips
INNER JOIN 
    sys.indexes i ON ips.object_id = i.object_id AND ips.index_id = i.index_id
WHERE 
    ips.avg_fragmentation_in_percent > 5
ORDER BY 
    ips.avg_fragmentation_in_percent DESC;

The key is to document each step and maintain rollback procedures. With proper backups (which your DBA already has), the risk is virtually nonexistent.

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When index fragmentation exceeds 95% in SQL Server (as measured by sys.dm_db_index_physical_stats), query performance degrades significantly. The fear of data loss during index maintenance is common but largely misplaced when proper procedures are followed.

The anxiety stems from several technical misunderstandings:

• Confusing physical reorganization with logical data modification
• Lack of awareness about transactionally-safe index operations
• Overestimating the risk during online operations

SQL Server provides multiple safeguards during index maintenance:

-- Example 1: Online index rebuild (Enterprise Edition)
ALTER INDEX IX_YourIndex ON dbo.YourTable 
REBUILD WITH (ONLINE = ON, MAXDOP = 4);

-- Example 2: Transactionally-safe offline operation
BEGIN TRANSACTION;
ALTER INDEX IX_YourIndex ON dbo.YourTable REORGANIZE;
COMMIT TRANSACTION;

Always verify these before maintenance:

-- 1. Check database recovery model
SELECT name, recovery_model_desc FROM sys.databases;

-- 2. Verify backup chain
RESTORE HEADERONLY FROM DISK = 'C:\Backups\YourDB.bak';

-- 3. Test in non-production first
USE YourDB_Test;
EXEC sp_estimate_data_compression_savings 'dbo', 'YourTable', NULL, NULL, 'ROW';

For Dynamics GP or similar systems:

• Schedule during maintenance windows
• Use WITH (WAIT_AT_LOW_PRIORITY) in SQL 2014+ to prevent blocking
• Monitor sys.dm_tran_locks during operation

A phased approach minimizes risk:

-- Phase 1: Reorganize moderately fragmented indexes (5-30%)
DECLARE @ReorgSQL NVARCHAR(MAX) = '';
SELECT @ReorgSQL = @ReorgSQL + 
    'ALTER INDEX ' + QUOTENAME(i.name) + ' ON ' + 
    QUOTENAME(s.name) + '.' + QUOTENAME(o.name) + 
    ' REORGANIZE;' + CHAR(13)
FROM sys.dm_db_index_physical_stats(DB_ID(), NULL, NULL, NULL, 'LIMITED') ps
JOIN sys.indexes i ON ps.object_id = i.object_id AND ps.index_id = i.index_id
JOIN sys.objects o ON ps.object_id = o.object_id
JOIN sys.schemas s ON o.schema_id = s.schema_id
WHERE ps.avg_fragmentation_in_percent BETWEEN 5 AND 30;

-- Phase 2: Rebuild severely fragmented indexes (>30%)
DECLARE @RebuildSQL NVARCHAR(MAX) = '';
SELECT @RebuildSQL = @RebuildSQL + 
    'ALTER INDEX ' + QUOTENAME(i.name) + ' ON ' + 
    QUOTENAME(s.name) + '.' + QUOTENAME(o.name) + 
    ' REBUILD WITH (ONLINE = ON, SORT_IN_TEMPDB = ON);' + CHAR(13)
FROM sys.dm_db_index_physical_stats(DB_ID(), NULL, NULL, NULL, 'LIMITED') ps
JOIN sys.indexes i ON ps.object_id = i.object_id AND ps.index_id = i.index_id
JOIN sys.objects o ON ps.object_id = o.object_id
JOIN sys.schemas s ON o.schema_id = s.schema_id
WHERE ps.avg_fragmentation_in_percent > 30;

Essential DMVs to track progress:

-- Live progress monitoring
SELECT 
    session_id,
    command,
    percent_complete,
    estimated_completion_time/1000/60 AS remaining_minutes
FROM sys.dm_exec_requests
WHERE command LIKE '%INDEX%';

-- Blocking analysis
SELECT * FROM sys.dm_os_waiting_tasks
WHERE blocking_session_id IS NOT NULL;