Index reorganisation

[Petemac21]

In the SQL Server Index and Statistics Maintenance solution here:

https://ola.hallengren.com/sql-server-index-and-statistics-maintenance.html

it states that "an index reorganization is not always possible". Under what circumstances would an index reorganisation not be possible?

[olahallengren]

ALTER INDEX ... REORGANIZE is not supported in the following scenarios:

1. Page locks is disabled on the index, sys.indexes.allow_page_locks = 0

2. It is a memory optimized table, sys.tables.is_memory_optimized = 1