STATUS . If the history list grows longer than the value of the  innodb_max_purge_lag  configuration option, each  DML  operation is delayed slightly to allow the purge operation to finish  flushing  the deleted records. Also known as  purge lag . See Also DML, flush, purge, purge lag, rollback segment, transaction, undo log.  Releasing empty blocks from a page. The  InnoDB transparent page compression  feature relies on hole punching support. For more information, see Section 15.9.2, “InnoDB Page Compression” . See Also sparse file, transparent page compression.  The network name of a database server, used to establish a  connection . Often specified in conjunction with a port . In some contexts, the IP address  127.0.0.1  works better than the special name  localhost  for accessing a database on the same server as the application. See Also connection, localhost, port.  A condition where a row, table, or internal data structure is accessed so frequently, requiring some form of locking or mutual exclusion, that it results in a performance or scalability issue. Although “hot”  typically indicates an undesirable condition, a  hot backup  is the preferred type of backup. See Also hot backup.  A backup taken while the database is running and applications are reading and writing to it. The backup involves more than simply copying data files: it must include any data that was inserted or updated while the backup was in process; it must exclude any data that was deleted while the backup was in process; and it must ignore any changes that were not committed. The Oracle product that performs hot backups, of  InnoDB  tables especially but also tables from  MyISAM  and other storage engines, is known as  MySQL Enterprise Backup . The hot backup process consists of two stages. The initial copying of the data files produces a  raw backup . The apply  step incorporates any changes to the database that happened while the backup was running. Applying the changes produces a  prepared  backup; these files are ready to be restored whenever necessary. See Also apply, MySQL Enterprise Backup, prepared backup, raw backup.  The data file for  file-per-table  tablespaces and general tablespaces. File-per-table tablespace  .ibd  files contain a single table and associated index data.  General tablespace .ibd  files may contain table and index data for multiple tables. The  .ibd  file extension does not apply to the  system tablespace , which consists of one or more  ibdata files . If a file-per-table tablespace or general tablespace is created with the  DATA DIRECTORY =  clause, the  .ibd  file is located at the specified path, outside the normal data directory. When a  .ibd  file is included in a compressed backup by the  MySQL Enterprise Backup  product, the compressed equivalent is a  .ibz  file. See Also database, file-per-table, general tablespace, ibdata file, .ibz file, innodb_file_per_table, MySQL Enterprise Backup, system tablespace. 6156 hole punching host hot hot backup .ibd file I