## transparent page compression 

 A feature added in MySQL 5.7.8 that permits page-level compression for InnoDB  tables that reside in file-per- table  tablespaces. Page compression is enabled by specifying the COMPRESSION  attribute with CREATE TABLE or ALTER TABLE . For more information, see Section 15.9.2, “InnoDB Page Compression” . 

See Also file-per-table, hole punching, sparse file. 

## transportable tablespace 

 A feature that allows a tablespace  to be moved from one instance to another. Traditionally, this has not been possible for InnoDB  tablespaces because all table data was part of the system tablespace . In MySQL 5.6 and higher, the FLUSH TABLES ... FOR EXPORT  syntax prepares an InnoDB  table for copying to another server; running ALTER TABLE ... DISCARD TABLESPACE  and ALTER TABLE ... IMPORT TABLESPACE  on the other server brings the copied data file into the other instance. A separate .cfg file , copied along with the .ibd file , is used to update the table metadata (for example the space ID ) as the tablespace is imported. See Section 15.6.1.3, “Importing InnoDB Tables”  for usage information. 

See Also .cfg file, .ibd file, space ID, system tablespace, tablespace. 

## troubleshooting 

 The process of determining the source of a problem. Some of the resources for troubleshooting MySQL problems include: 

•Section 2.10.2.1, “Troubleshooting Problems Starting the MySQL Server” 

•Section 6.2.21, “Troubleshooting Problems Connecting to MySQL” 

•Section B.3.3.2, “How to Reset the Root Password” 

•Section B.3.2, “Common Errors When Using MySQL Programs” 

•Section 15.21, “InnoDB Troubleshooting” . 

## truncate 

 A DDL  operation that removes the entire contents of a table, while leaving the table and related indexes intact. Contrast with drop . Although conceptually it has the same result as a DELETE  statement with no WHERE  clause, it operates differently behind the scenes: InnoDB  creates a new empty table, drops the old table, then renames the new table to take the place of the old one. Because this is a DDL operation, it cannot be rolled back . 

If the table being truncated contains foreign keys  that reference another table, the truncation operation uses a slower method of operation, deleting one row at a time so that corresponding rows in the referenced table can be deleted as needed by any ON DELETE CASCADE  clause. (MySQL 5.5 and higher do not allow this slower form of truncate, and return an error instead if foreign keys are involved. In this case, use a DELETE  statement instead. See Also DDL, drop, foreign key, rollback. 

## truststore 

See Also SSL. 

## tuple 

 A technical term designating an ordered set of elements. It is an abstract notion, used in formal discussions of database theory. In the database field, tuples are usually represented by the columns of a table row. They could also be represented by the result sets of queries, for example, queries that retrieved only some columns of a table, or columns from joined tables. 

See Also cursor. 

## two-phase commit 

 An operation that is part of a distributed transaction , under the XA  specification. (Sometimes abbreviated as 2PC.) When multiple databases participate in the transaction, either all databases commit  the changes, or all databases roll back  the changes. 

