B Automatic and Manual Locking Mechanisms During SQL Operations
This appendix describes mechanisms that lock data either automatically or as specified by the user during SQL statements. For a general discussion of locking mechanisms in the context of data concurrency and consistency, see Oracle Database Concepts.
This appendix contains the following sections:
List of Nonblocking DDLs
Nonblocking DDLs added at each release from 11.2 to 12.2.0.2 are listed here.
Release 11.2
The following nonblocking DDLs are added as of Release 11.2. Some nonblocking DDLs are downgraded to blocking in the presence of supplemental logging.
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create index online
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alter index rebuild online
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alter index rebuild partition online
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alter index rebuild subpartition online
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alter index visible / novisible
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alter table add column not null with default value
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alter table add constraint enable novalidate
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alter table modify constraint validate
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alter table add column (without any default)
Release 12.1
The following nonblocking DDLs are added as of Release 12.1. Some nonblocking DDLs are downgraded to blocking in the presence of supplemental logging.
List of Nonblocking DDLs Added in 12.1
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drop index online
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alter index unusable online
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alter table move partition online
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alter table move subpartition online
List of Nonblocking DDLs Added in 12.1 that Downgrade to Blocking During Supplemental Logging
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alter table set unused column online
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alter table drop constraint online
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alter table modify column visible / invisible
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alter table add nullable column with default value
Release 12.2.0.1
List of Nonblocking DDLs Added in 12.2.0.1
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alter table split partition [subpartition] online
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alter table move online (move of a non-partitioned table)
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alter table modify partition by .. online (to convert a non-partitioned table to partitioned state)
Release 12.2.0.2
List of Nonblocking DDLs Added in 12.2.0.2
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Alter table merge partition online
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alter table modify partition by .. online (to change the partitioning schema of a table)