ALTER INDEX

Purpose

Use the ALTER INDEX statement to change or rebuild an existing index.

Prerequisites

The index must be in your own schema or you must have ALTER ANY INDEX system privilege.

To execute the MONITORING USAGE clause, the index must be in your own schema.

To modify a domain index, you must have EXECUTE object privilege on the indextype of the index.

Schema object privileges are granted on the parent index, not on individual index partitions or subpartitions.

You must have tablespace quota to modify, rebuild, or split an index partition or to modify or rebuild an index subpartition.

Syntax

alter_index::=

Text description of alter_index

(deallocate_unused_clause::=, allocate_extent_clause::=, parallel_clause::=, physical_attributes_clause::=, logging_clause::=, rebuild_clause::=, alter_index_partitioning::=)

deallocate_unused_clause::=

Text description of deallocate_unused_clause

allocate_extent_clause::=

Text description of allocate_extent_clause

parallel_clause::=

Text description of parallel_clause

physical_attributes_clause::=

Text description of physical_attributes_clause

(storage_clause::=)

logging_clause::=

Text description of logging_clause

rebuild_clause::=

Text description of rebuild_clause

(physical_attributes_clause::=, key_compression::=, logging_clause::=)

key_compression::=

Text description of key_compression

alter_index_partitioning::=

Text description of alter_index_partitioning

(modify_index_default_attrs::=, modify_index_partition::=, rename_index_partition::=, drop_index_partition::=, split_index_partition::=, modify_index_subpartition::=)

modify_index_default_attrs::=

Text description of modify_index_default_attrs

(physical_attributes_clause::=, logging_clause::=)

modify_index_partition::=

Text description of modify_index_partition

(physical_attributes_clause::=, logging_clause::=, allocate_extent_clause::=, deallocate_unused_clause::=)

rename_index_partition::=

Text description of rename_index_partition

drop_index_partition::=

Text description of drop_index_partition

split_index_partition::=

Text description of split_index_partition

(parallel_clause::=)

index_partition_description::=

Text description of index_partition_description

(key_compression::=)

segment_attributes_clause::=

Text description of segment_attributes_clause

(physical_attributes_clause::=, logging_clause::=)

modify_index_subpartition::=

Text description of modify_index_subpartition

(allocate_extent_clause::=, deallocate_unused_clause::=)

Semantics

schema

Specify the schema containing the index. If you omit schema, Oracle assumes the index is in your own schema.

index

Specify the name of the index to be altered.

Restrictions on Modifying Indexes

• If index is a domain index, you can specify only the PARAMETERS clause, the RENAME clause, the rebuild_clause (with or without the PARAMETERS clause), the parallel_clause, or the UNUSABLE clause. No other clauses are valid.
• You cannot alter or rename a domain index that is marked LOADING or FAILED. If an index is marked FAILED, the only clause you can specify is REBUILD.

  See Also: Oracle9i Data Cartridge Developer's Guide for information on the LOADING and FAILED states of domain indexes

deallocate_unused_clause

Use the deallocate_unused_clause to explicitly deallocate unused space at the end of the index and make the freed space available for other segments in the tablespace.

If index is range-partitioned or hash-partitioned, Oracle deallocates unused space from each index partition. If index is a local index on a composite-partitioned table, Oracle deallocates unused space from each index subpartition.

Restrictions on Deallocating Space

• You cannot specify this clause for an index on a temporary table.
• You cannot specify this clause and also specify the rebuild_clause.

  See Also: deallocate_unused_clause for a full description of this clause

KEEP integer

The KEEP clause lets you specify the number of bytes above the high water mark that the index will have after deallocation. If the number of remaining extents are less than MINEXTENTS, then MINEXTENTS is set to the current number of extents. If the initial extent becomes smaller than INITIAL, then INITIAL is set to the value of the current initial extent. If you omit KEEP, all unused space is freed.

allocate_extent_clause

The allocate_extent_clause lets you explicitly allocate a new extent for the index. For a local index on a hash-partitioned table, Oracle allocates a new extent for each partition of the index.

Restriction on Allocating Extents

You cannot specify this clause for an index on a temporary table or for a range-partitioned or composite-partitioned index.

parallel_clause

Use the PARALLEL clause to change the default degree of parallelism for queries and DML on the index.

Restriction on Parallelizing Indexes

You cannot specify this clause for an index on a temporary table.

NOPARALLEL

Specify NOPARALLEL for serial execution. This is the default.

PARALLEL

Specify PARALLEL if you want Oracle to select a degree of parallelism equal to the number of CPUs available on all participating instances times the value of the PARALLEL_THREADS_PER_CPU initialization parameter.

PARALLEL integer

Specification of integer indicates the degree of parallelism, which is the number of parallel threads used in the parallel operation. Each parallel thread may use one or two parallel execution servers. Normally Oracle calculates the optimum degree of parallelism, so it is not necessary for you to specify integer.

physical_attributes_clause

Use the physical_attributes_clause to change the values of parameters for a nonpartitioned index, all partitions and subpartitions of a partitioned index, a specified partition, or all subpartitions of a specified partition.

Restrictions on Index Physical Attributes

• You cannot specify this clause for an index on a temporary table.
• You cannot specify the PCTUSED parameter at all when altering an index.
• You can specify the PCTFREE parameter only as part of the rebuild_clause, the modify_index_default_attrs clause, or the split_partition_clause.

storage_clause

Use the storage_clause to change the storage parameters for a nonpartitioned index, index partition, or all partitions of a partitioned index, or default values of these parameters for a partitioned index.

logging_clause

Use the logging_clause to specify whether subsequent Direct Loader (SQL*Loader) and direct-path INSERT operations against a nonpartitioned index, a range or hash index partition, or all partitions or subpartitions of a composite-partitioned index will be logged (LOGGING) or not logged (NOLOGGING) in the redo log file.

An index segment can have logging attributes different from those of the base table and different from those of other index segments for the same base table.

Restriction on Index Logging

You cannot specify this clause for an index on a temporary table.

RECOVERABLE | UNRECOVERABLE

These keywords are deprecated and have been replaced with LOGGING and NOLOGGING, respectively. Although RECOVERABLE and UNRECOVERABLE are supported for backward compatibility, Oracle Corporation strongly recommends that you use the LOGGING and NOLOGGING keywords.

RECOVERABLE is not a valid keyword for creating partitioned tables or LOB storage characteristics. UNRECOVERABLE is not a valid keyword for creating partitioned or index-organized tables. Also, it can be specified only with the AS subquery clause of CREATE INDEX.

rebuild_clause

Use the rebuild_clause to re-create an existing index or one of its partitions or subpartitions. If index is marked UNUSABLE, a successful rebuild will mark it USABLE. For a function-based index, this clause also enables the index. If the function on which the index is based does not exist, the rebuild statement will fail.

Restrictions on Rebuilding Indexes

• You cannot rebuild an index on a temporary table.
• You cannot rebuild a bitmap index that is marked INVALID. Instead, you must drop and then re-create it.
• You cannot rebuild an entire partitioned index. You must rebuild each partition or subpartition, as described for the PARTITION clause.
• You cannot also specify the deallocate_unused_clause in this statement.
• You cannot change the value of the PCTFREE parameter for the index as a whole (ALTER INDEX) or for a partition (ALTER INDEX ... MODIFY PARTITION). You can specify PCTFREE in all other forms of the ALTER INDEX statement.
• For a domain index:
  • You can specify only the PARAMETERS clause (either for the index or for a partition of the index) or the parallel_clause. No other rebuild clauses are valid.
  • You can rebuild the index only if index is not marked IN_PROGRESS.
  • You can rebuild the index partitions only if index is not marked IN_PROGRESS or FAILED and partition is not marked IN_PROGRESS.
• You cannot rebuild a local index, but you can rebuild a partition of a local index (ALTER INDEX ... REBUILD PARTITION).
• For a local index on a hash partition or subpartition, the only parameter you can specify is TABLESPACE.

PARTITION Clause

Use the PARTITION clause to rebuild one partition of an index. You can also use this clause to move an index partition to another tablespace or to change a create-time physical attribute.

Restriction on Rebuilding Partitions

You cannot specify this clause for a local index on a composite-partitioned table. Instead, use the REBUILD SUBPARTITION clause.

SUBPARTITION Clause

Use the SUBPARTITION clause to rebuild one subpartition of an index. You can also use this clause to move an index subpartition to another tablespace. If you do not specify TABLESPACE, the subpartition is rebuilt in the same tablespace.

Restrictions on Modifying Index Subpartitions

• The only parameters you can specify for a subpartition are TABLESPACE and the parallel_clause.
• You cannot rebuild the subpartition of a list partition.

REVERSE | NOREVERSE

Indicate whether the bytes of the index block are stored in reverse order:

• REVERSE stores the bytes of the index block in reverse order and excludes the rowid when the index is rebuilt.
• NOREVERSE stores the bytes of the index block without reversing the order when the index is rebuilt. Rebuilding a REVERSE index without the NOREVERSE keyword produces a rebuilt, reverse-keyed index.

Restrictions on Reverse Indexes

• You cannot reverse a bitmap index or an index-organized table.
• You cannot specify REVERSE or NOREVERSE for a partition or subpartition.

  See Also: "Storing Index Blocks in Reverse Order: Example"

parallel_clause

Use the parallel_clause to parallelize the rebuilding of the index.

TABLESPACE Clause

Specify the tablespace where the rebuilt index, index partition, or index subpartition will be stored. The default is the default tablespace where the index or partition resided before you rebuilt it.

COMPRESS | NOCOMPRESS

Specify COMPRESS to enable key compression, which eliminates repeated occurrence of key column values. Use integer to specify the prefix length (number of prefix columns to compress).

• For unique indexes, the range of valid prefix length values is from 1 to the number of key columns minus 1. The default prefix length is the number of key columns minus 1.
• For nonunique indexes, the range of valid prefix length values is from 1 to the number of key columns. The default prefix length is number of key columns.

Oracle compresses only nonpartitioned indexes that are nonunique or unique indexes of at least two columns.

Specify NOCOMPRESS to disable key compression. This is the default.

Restriction on Key Compression

You cannot specify COMPRESS for a bitmap index.

ONLINE Clause

Specify ONLINE to allow DML operations on the table or partition during rebuilding of the index.

Restrictions on ONLINE

• Parallel DML is not supported during online index building. If you specify ONLINE and then issue parallel DML statements, Oracle returns an error.
• You cannot specify ONLINE for a bitmap index or a cluster index.
• For a unique index on an index-organized table, the number of index key columns plus the number of primary key columns in the index-organized table cannot exceed 32.

COMPUTE STATISTICS Clause

Specify COMPUTE STATISTICS if you want to collect statistics at relatively little cost during the rebuilding of an index. These statistics are stored in the data dictionary for ongoing use by the optimizer in choosing a plan of execution for SQL statements.

The types of statistics collected depend on the type of index you are rebuilding.

Additional methods of collecting statistics are available in PL/SQL packages and procedures

logging_clause

Specify whether the ALTER INDEX ... REBUILD operation will be logged.

PARAMETERS Clause

The PARAMETERS clause applies only to domain indexes. This clause specifies the parameter string that is passed uninterpreted to the appropriate ODCI indextype routine. The maximum length of the parameter string is 1000 characters.

If you are altering or rebuilding an entire index, the string must refer to index-level parameters. If you are rebuilding a partition of the index, the string must refer to partition-level parameters.

If index is marked UNUSABLE, modifying the parameters alone does not make it USABLE. You must also rebuild the UNUSABLE index to make it usable.

Restrictions on the PARAMETERS Clause

• You can specify this clause only for a domain index.
• You can modify index partitions only if index is not marked IN_PROGRESS or FAILED, no index partitions are marked IN_PROGRESS, and the partition being modified is not marked FAILED.

  See Also: Oracle9i Data Cartridge Developer's Guide for more information on indextype routines. CREATE INDEX for more information on domain indexes

ENABLE Clause

ENABLE applies only to a function-based index that has been disabled because a user-defined function used by the index was dropped or replaced. This clause enables such an index if these conditions are true:

• The function is currently valid
• The signature of the current function matches the signature of the function when the index was created
• The function is currently marked as DETERMINISTIC

Restriction on Enabling Function-based Indexes

You cannot specify any other clauses of ALTER INDEX in the same statement with ENABLE.

DISABLE Clause

DISABLE applies only to a function-based index. This clause enables you to disable the use of a function-based index. You might want to do so, for example, while working on the body of the function. Afterward you can either rebuild the index or specify another ALTER INDEX statement with the ENABLE keyword.

UNUSABLE Clause

Specify UNUSABLE to mark the index or index partition(s) or index subpartition(s) UNUSABLE. An unusable index must be rebuilt, or dropped and re-created, before it can be used. While one partition is marked UNUSABLE, the other partitions of the index are still valid. You can execute statements that require the index if the statements do not access the unusable partition. You can also split or rename the unusable partition before rebuilding it.

Restriction on Marking Indexes Unusable

You cannot specify this clause for an index on a temporary table.

RENAME Clause

Use this clause to rename an index. The new_index_name is a single identifier and does not include the schema name.

Restriction on Renaming Indexes

For a domain index, neither index nor any partitions of index can be marked IN_PROGRESS or FAILED.

COALESCE Clause

Specify COALESCE to instruct Oracle to merge the contents of index blocks where possible to free blocks for reuse.

Restrictions on Coalescing Index Blocks

• You cannot specify this clause for an index on a temporary table.
• Do not specify this clause for the primary key index of an index-organized table. Instead use the COALESCE clause of ALTER TABLE.

  See Also: Oracle9i Database Administrator's Guide for more information on space management and coalescing indexes COALESCE for information on coalescing space of an index-organized table

MONITORING USAGE | NOMONITORING USAGE

Use this clause to determine whether Oracle should monitor index use.

• Specify MONITORING USAGE to begin monitoring the index. Oracle first clears existing information on index usage, and then monitors the index for use until a subsequent ALTER INDEX ... NOMONITORING USAGE statement is executed.
• To terminate monitoring of the index, specify NOMONITORING USAGE.

To see whether the index has been used since this ALTER INDEX ... NOMONITORING USAGE statement was issued, query the USED column of the V$OBJECT_USAGE dynamic performance view.

UPDATE BLOCK REFERENCES Clause

The UPDATE BLOCK REFERENCES clause is valid only for normal and domain indexes on index-organized tables. Specify this clause to update all the stale "guess" data block addresses stored as part of the index row with the correct database address for the corresponding block identified by the primary key.

Restriction on UPDATE BLOCK REFERENCES

You cannot combine this clause with any other clause of ALTER INDEX.

alter_index_partitioning

The partitioning clauses of the ALTER INDEX statement are valid only for partitioned indexes.

Restrictions on Altering Index Partitions

• You cannot specify any of these clauses for an index on a temporary table.
• You can combine several operations on the base index into one ALTER INDEX statement (except RENAME and REBUILD), but you cannot combine partition operations with other partition operations or with operations on the base index.

modify_index_default_attrs

Specify new values for the default attributes of a partitioned index.

Restriction on Modifying Partition Default Attributes

The only attribute you can specify for an index on a hash-partitioned or composite-partitioned table is TABLESPACE.

TABLESPACE

Specify the default tablespace for new partitions of an index or subpartitions of an index partition.

logging_clause

Specify the default logging attribute of a partitioned index or an index partition.

FOR PARTITION

Use the FOR PARTITION clause to specify the default attributes for the subpartitions of a partition of a local index on a composite-partitioned table.

Restriction on FOR PARTITION

You cannot specify FOR PARTITION for a list partition.

modify_index_partition

Use the modify_index_partition clause to modify the real physical attributes, logging attribute, or storage characteristics of index partition partition or its subpartitions.

UPDATE BLOCK REFERENCES

The UPDATE BLOCK REFERENCES clause is valid only for normal indexes on index-organized tables. Use this clause to update all stale "guess" data block addresses stored in the secondary index partition.

Restrictions on UPDATE BLOCK REFERENCES

• You cannot specify the physical_attributes_clause for an index on a hash-partitioned table.
• You cannot specify UPDATE BLOCK REFERENCES with any other clause in ALTER INDEX.

  Note: If the index is a local index on a composite-partitioned table, the changes you specify here will override any attributes specified earlier for the subpartitions of index, as well as establish default values of attributes for future subpartitions of that partition. To change the default attributes of the partition without overriding the attributes of subpartitions, use ALTER TABLE ... MODIFY DEFAULT ATTRIBUTES OF PARTITION.

  See Also: "Marking an Index Unusable: Examples"

rename_index_partition

Use the rename_index_partition clauses to rename index partition or subpartition to new_name.

Restrictions on Renaming Index Partitions

• You cannot rename the subpartition of a list partition.
• For a partition of a domain index, index must not be marked IN_PROGRESS or FAILED, none of the partitions can be marked IN_PROGRESS, and the partition you are renaming must not be marked FAILED.

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  See Also: "Renaming an Index Partition: Example"

drop_index_partition

Use the drop_index_partition clause to remove a partition and the data in it from a partitioned global index. When you drop a partition of a global index, Oracle marks the index's next partition UNUSABLE. You cannot drop the highest partition of a global index.

split_index_partition

Use the split_index_partition clause to split a partition of a global partitioned index into two partitions, adding a new partition to the index.

Splitting a partition marked UNUSABLE results in two partitions, both marked UNUSABLE. You must rebuild the partitions before you can use them.

Splitting a usable partition results in two partitions populated with index data. Both new partitions are usable.

AT Clause

Specify the new noninclusive upper bound for split_partition_1. The value_list must evaluate to less than the presplit partition bound for partition_name_old and greater than the partition bound for the next lowest partition (if there is one).

INTO Clause

Specify (optionally) the name and physical attributes of each of the two partitions resulting from the split.

modify_index_subpartition

Use the modify_index_subpartition clause to mark UNUSABLE or allocate or deallocate storage for a subpartition of a local index on a composite-partitioned table. All other attributes of such a subpartition are inherited from partition-level default attributes.

Examples

Storing Index Blocks in Reverse Order: Example

The following statement rebuilds index ord_customer_ix (created in "Creating an Index: Example") so that the bytes of the index block are stored in reverse order:

ALTER INDEX ord_customer_ix REBUILD REVERSE;

Collecting Index Statistics: Example

The following statement collects statistics on the nonpartitioned ord_customer_ix index:

ALTER INDEX ord_customer_ix REBUILD COMPUTE STATISTICS;

The type of statistics collected depends on the type of index you are rebuilding.

Rebuilding an Index in Parallel: Example

The following statement causes the index to be rebuilt from the existing index by using parallel execution processes to scan the old and to build the new index:

ALTER INDEX ord_customer_ix REBUILD PARALLEL;

Modifying Real Attributes: Example

The following statement alters the oe.cust_lname_ix index so that future data blocks within this index use 5 initial transaction entries and an incremental extent of 100 kilobytes:

/* Unless you change the default tablespace of sample user oe,
   or specify different tablespace storage for the index, this
   example fails because the default tablespace originally assigned
   to oe is locally managed.
*/
ALTER INDEX oe.cust_lname_ix  
    INITRANS 5  
    STORAGE (NEXT 100K); 

If the oe.cust_lname_ix index were partitioned, this statement would also alter the default attributes of future partitions of the index. New partitions added in the future would then use 5 initial transaction entries and an incremental extent of 100K.

Enabling Parallel Queries: Example

The following statement sets the parallel attributes for index upper_ix (created in "Creating a Function-Based Index: Example") so that scans on the index will be parallelized:

ALTER INDEX upper_ix PARALLEL;

Renaming an Index: Example

The following statement renames an index:

ALTER INDEX upper_ix RENAME TO upper_name_ix;

Marking an Index Unusable: Examples

The following statements use the cost_ix index, which was created in "Creating a Global Partitioned Index: Example". Partition p1 of that index was dropped in "Dropping an Index Partition: Example". The first statement marks the marks index partition p2 as UNUSABLE:

ALTER INDEX cost_ix
   MODIFY PARTITION p2 UNUSABLE;

The next statement marks the entire index cost_ix as UNUSABLE:

ALTER INDEX cost_ix UNUSABLE;

Rebuilding Unusable Index Partitions: Example

The following statements rebuild partitions p2 and p3 of the cost_ix index, making the index once more usable: The rebuilding of partition p3 will not be logged:

ALTER INDEX cost_ix 
   REBUILD PARTITION p2;
ALTER INDEX cost_ix
   REBUILD PARTITION p3 NOLOGGING;

Changing MAXEXTENTS: Example

The following statement changes the maximum number of extents for partition p3 and changes the logging attribute:

/* This example will fail if the tablespace in which partition p3
   resides is locally managed.
*/
ALTER INDEX cost_ix MODIFY PARTITION p3
   STORAGE(MAXEXTENTS 30) LOGGING;

Renaming an Index Partition: Example

The following statement renames an index partition of the cost_ix index (created in "Creating a Global Partitioned Index: Example"):

ALTER INDEX cost_ix
   RENAME PARTITION p3 TO p3_Q3;

Splitting a Partition: Example

The following statement splits partition p2 of index cost_ix (created in "Creating a Global Partitioned Index: Example") into p2a and p2b:

ALTER INDEX cost_ix
   SPLIT PARTITION p2 AT (1500) 
   INTO ( PARTITION p2a TABLESPACE tbs_01 LOGGING,
          PARTITION p2b TABLESPACE tbs_02);

Dropping an Index Partition: Example

The following statement drops index partition p1 from the cost_ix index:

ALTER INDEX cost_ix
   DROP PARTITION p1;

Modifying Default Attributes: Example

The following statement alters the default attributes of local partitioned index prod_idx, which was created in "Creating an Index on a Hash-Partitioned Table: Example.". New partitions added in the future will use 5 initial transaction entries and an incremental extent of 100K:

ALTER INDEX prod_idx
      MODIFY DEFAULT ATTRIBUTES INITRANS 5 STORAGE (NEXT 100K);