Partitions are marked suspect for two reasons:
A sort order or character set change on a range-partitioned table
A cross-platform dump and load with a hash-partitioned table
If the table is marked with suspect partitions:
All updates and cursor activities are suspended on this table.
No alter table commands, except partition by, are allowed. create index and drop index are not allowed on a table with suspect partitions.
The select command is allowed on tables containing suspect partitions. However, the optimizer treats such tables as round-robin partitioned tables, to avoid using the possibly corrupt partition condition.
