可能導致index unusable的維護操作

Six types of maintenance operationscan mark index partitions INDEX UNUSABLE.
In all cases, you must rebuild the index partitions when theoperation is
complete.

  1)   Operations like Import Partition or conventionalpath SQL*Loader
       that offer an option to bypass local indexmaintenance.  When the
       Import is complete, the affected local index partitions aremarked
       IU.

  2)   Direct path SQL*Loader leaves affected localindex partitions and
       global indexes in an IU state if the index is out of datewith
       respect to the data that it indexes.  The indexcan be out of date
       for the following reasons:

       a)  The index was not maintained during the loaddue to a space
           management error (for example, out of extents ORA-1653 or
           ORA-1652).

       b)  The user requested the SKIP_INDEX_MAINTENANCEclause.

  3)   Partition maintenance operations like ALTER TABLEMOVE PARTITION
       that change rowids.  These operations mark theaffected local index
       partition and all global index partitions IU.

  4)   Partition maintenance operations like ALTER TABLETRUNCATE PARTITION
       or DROP PARTITION that remove rows from thetable.  These operations
       mark the affected local index partition and all global index
       partitions IU.

  5)   Partition maintenance operations like ALTER TABLESPLIT PARTITION
       that modify the partition definition of local indexes but donot
       automatically rebuild the index data to match the newdefinitions.
       These operations mark the affected local index partitionsIU.  ALTER
       TABLE SPLIT PARTITION also marks all global index partitionsIU
       because it results in changes to rowids.

  6)   Index maintenance operations like ALTER INDEXSPLIT PARTITION that
       modify the partitioning definition of the index but do not
       automatically rebuild the affected partitions. These operations
       mark the affected index partitions IU.  However,if you split a
       USABLE partition of a global index, resulting partitions arecreated
       USABLE.  If the partition that was split wasmarked IU, then so are
       the partitions resulting from the split.  Notethat dropping a
       partition of a global index that is either IU or is not emptycauses
       the next partition of the index to become IU.


The ALTER INDEX REBUILD PARTITION statement can be used toregenerate a single
partition in a local or global partitioned index. This saves you from having
to perform DROP INDEX and then CREATE INDEX, which would affect allpartitions
in the index.

 

To prevent indexes to become unusable duringpartition maintenance operations, you can use 'update globalindexes' clause in 9.2,
'update global indexes' or 'update indexes' clauses in 10g andabove. For more details please consult the SQL Reference at ALTERTABLE for more details. Also, there are certain scenarios where theindexes are not marked unusable, e.g. DROP, TRUNCATE partitionnormally marks global indexes unusable, but not when the partitionto be dropped/truncated is empty. Similar with SPLIT partition,when the split results in adding a new empty partition to the table(all the rows of the partition to be split goes into one of theresulting partition, and the other partition remains empty).