A database directory contains the following, as shown in :
- log directory
Contains files that make up the database transaction
log, used internally for data recovery (not the same thing as the error log).
- seg0 directory
Contains one file for each user table, system
table, and index (known as conglomerates).
- service.properties file
A text file with internal configuration
information.
- tmp directory
(might not exist.) A temporary directory used
by for large sorts
and deferred updates and deletes. Sorts are used by a variety of SQL statements.
For databases on read-only media, you might need to set a property to change
the location of this directory. See "Creating Databases
for Read-Only Use".
- jar directory
(might not exist.) A directory in which jar
files are stored when you use database class loading.
Read-only database directories
can be archived (and compressed, if desired) into jar or zip files. For more
information, see .
<ph conref="devconrefs.dita#prod/productshortname"></ph> database
directories contain files and directories used by the software.
A Derby database directory
containing files and directories.
imposes relatively
few limitations on the number and size of databases and database objects.
The following table shows some size limitations of databases
and database objects:
Size Limits to Derby
Database Objects
Type of Object
Limit
tables per database
java.lang.Long.MAX_VALUE Some operating systems
impose a limit to the number of files allowed in a single directory.
indexes per table
32,767 or storage
columns per table
1,012
number of columns on an index key
16
rows per table
no limit
size of table
no limit Some operating systems impose a limit on the size
of a single file.
size of row
no limit--rows can span pages. Rows cannot span tables
so some operating systems impose a limit on the size of a single file, and
therefore limit the size of a table and size of a row in that table.
For a complete list of restrictions on databases
and database objects, see the .