The database file   This file holds the entire contents of your database. A single file can contain a single database, or you can add up to 12 dbspaces, which are additional files holding portions of the same database. You choose a location for the database file and dbspaces. The database file typically has the extension .db.

The transaction log   This file holds a record of the changes made to the database, and is necessary for synchronization and recovery of the information in your database in the event of a failure. The transaction log typically has the extension .log. See The transaction log.

The temporary file   The database server uses the temporary file during a database session when SQL Anywhere needs more space than is available to it in the cache for such operations as sorting and forming unions. When the database server needs this space, it generally uses it intensively. The overall performance of your database becomes heavily dependent on the speed of the device containing the temporary file. The database server discards this file once the database shuts down—even if the database server remains running. The temporary file has a server-generated name with the extension .tmp.

The location of the temporary file can be specified when starting the database server using the -dt server option. If you do not specify the location of the temporary file when starting the database server, the following environment variables are checked, in order:

• SATMP environment variable
• TMP environment variable
• TMPDIR environment variable
• TEMP environment variable

If none of these environment variables are defined, SQL Anywhere places its temporary file in the current directory on Windows operating systems, or in the /tmp directory on Unix.

The database server creates, maintains, and removes the temporary file. You only need to ensure that there is enough free space available for the temporary file. You can obtain information about the space available for the temporary file using the sa_disk_free_space procedure. See sa_disk_free_space system procedure.

Predefined dbspace files   These files store your data and other files used by the database. See Predefined dbspaces.

Dbspace files   You can spread your data over several separate files, in addition to the database file. See Additional dbspaces considerations.

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