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•To avoid accidentally making the table unavailable for reads, writes, or both, during an in-place ALTER TABLE  operation, specify a clause on the ALTER TABLE  statement such as LOCK=NONE  (permit reads and writes) or LOCK=SHARED  (permit reads). The operation halts immediately if the requested level of concurrency is not available. 

•To compare performance between algorithms, run a statement with ALGORITHM=INSTANT , ALGORITHM=INPLACE  and ALGORITHM=COPY . You can also run a statement with the old_alter_table  configuration option enabled to force the use of ALGORITHM=COPY . 

•To avoid tying up the server with an ALTER TABLE  operation that copies the table, include ALGORITHM=INSTANT  or ALGORITHM=INPLACE . The statement halts immediately if it cannot use the specified algorithm. 

## 15.12.1 Online DDL Operations 

Online support details, syntax examples, and usage notes for DDL operations are provided under the following topics in this section. 

## Index Operations 

•Index Operations 

•Primary Key Operations 

•Column Operations 

•Generated Column Operations 

•Foreign Key Operations 

•Table Operations 

•Tablespace Operations 

•Partitioning Operations 

The following table provides an overview of online DDL support for index operations. An asterisk indicates additional information, an exception, or a dependency. For details, see Syntax and Usage Notes. 

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