See Also cardinality, query.  A type of read operation used for  UPDATE  statements, that is a combination of  READ COMMITTED  and consistent read . When an  UPDATE  statement examines a row that is already locked,  InnoDB  returns the latest committed version to MySQL so that MySQL can determine whether the row matches the  WHERE  condition of the  UPDATE . If the row matches (must be updated), MySQL reads the row again, and this time  InnoDB  either locks it or waits for a lock on it. This type of read operation can only happen when the transaction has the READ COMMITTED  isolation level . See Also consistent read, isolation level, READ COMMITTED.  The  isolation level  that uses the most conservative locking strategy, to prevent any other  transactions  from inserting or changing data that was read by this transaction, until it is finished. This way, the same query can be run over and over within a transaction, and be certain to retrieve the same set of results each time. Any attempt to change data that was committed by another transaction since the start of the current transaction, cause the current transaction to wait. This is the default isolation level specified by the SQL standard. In practice, this degree of strictness is rarely needed, so the default isolation level for  InnoDB  is the next most strict,  REPEATABLE READ . See Also ACID, consistent read, isolation level, locking, REPEATABLE READ, transaction.  Dictionary object metadata in serialized form. SDI is stored in  JSON  format. As of MySQL 8.0.3, SDI is present in all  InnoDB  tablespace files except for temporary tablespace and undo tablespace files. The presence of SDI in tablespace files provides metadata redundancy. For example, dictionary object metadata can be extracted from tablespace files using the  ibd2sdi  utility if the data dictionary becomes unavailable. For a  MyISAM  table, SDI is stored in a  .sdi  metadata file in the schema directory. An SDI metadata file is required to perform an  IMPORT TABLE  operation. See Also file-per-table, general tablespace, system tablespace, tablespace.  A type of program that runs continuously, waiting to receive and act upon requests from another program (the client ). Because often an entire computer is dedicated to running one or more server programs (such as a database server, a web server, an application server, or some combination of these), the term  server  can also refer to the computer that runs the server software. See Also client, mysqld.  A  prepared statement  managed by the MySQL server. Historically, issues with server-side prepared statements led  Connector/J  and  Connector/PHP  developers to sometimes use  client-side prepared statements  instead. With modern MySQL server versions, server-side prepared statements are recommended for performance, scalability, and memory efficiency. See Also client-side prepared statement, Connector/J, Connector/PHP, prepared statement. See Also Connector/J.  A  temporary tablespace  that stores user-created  temporary tables  and internal temporary tables created by the optimizer  when  InnoDB  is configured as the on-disk storage engine for internal temporary tables. semi-consistent read SERIALIZABLE serialized dictionary information (SDI) server server-side prepared statement servlet session temporary tablespace 6186