ASA Database Administration Guide
  Working with Database Files

Overview of database files

Basic database files 

Each database has the following files associated with it.

• The database file    This file holds the database information. It typically has the extension .db.

  For information on creating databases, see Working with databases.

• The transaction log    This file holds a record of the changes made to the database, and is necessary for recovery and replication. It typically has the extension .log.

  For information on the transaction log, see Backup and Data Recovery.

• The temporary file    The database server uses the temporary file to hold information needed during a database session. The database server disregards this file once the database shuts down—even if the server remains running. The file has a server-generated name with the extension .tmp.

  The temporary file is held in a location determined by an environment variable.

  The following environment variables are checked, in order:

  • ASTMP

  • TMP

  • TMPDIR

  • TEMP

  If none of these is defined, Adaptive Server Anywhere places its temporary file in the current directory on Windows operating systems, or in the /tmp/.SQLAnywhere directory on UNIX.

  The server creates, maintains, and removes the temporary file. You only need to ensure that there is enough free space available for the temporary file.

Additional files 

Other files can also become part of a database system, including:

• Additional database files    You can spread your data over several separate files. These additional files are called dbspaces.

  For information on dbspaces, see CREATE DBSPACE statement.

• Transaction log mirror files    For additional security, you can create a mirror copy of the transaction log. This file typically has the extension .mlg.

  For information on mirrored transaction logs, see Transaction log mirrors.

• Write files    If the database file you are working with is designated read-only (for example, because it is distributed on CD-ROM), you can use an additional write file to hold changes you make to the data. However, note that you can only use write files with read-only database files, not with a server running in read-only mode. Running the server in read-only mode allows no changes to the database file whatsoever.

• Compressed database files    You can compress a database file. The resulting file is read only, but can be used in conjunction with a write file. Compressed database files are used in place of the actual database file.

  For information on compression, see The Compression utility.