4. Creating, Running and Connecting to Databases

4.1. Creating a database

When you ask Adaptive Server Anywhere to create a database, it creates the main database file, which contains the following objects, among others:

• user tables

• indexes

• views

• system tables

The maximum size of a database file depends on your file system and the page size you choose. Database files are limited to 256 million database pages or the filesize limit, whichever is reached first. UNIX files can be as large as 1 Tb, in some cases-see the Physical Limitations chapter of the Adaptive Server Anywhere Reference Manual or your Linux documentation for more information. You can set pages to be 1, 2, 4, 8, 16, or 32 kb in size, but it is not recommended that you use a page size of 1 kb. The default page size is 2 kb.

By default, Adaptive Server Anywhere also creates a file called the transaction log. Besides improving performance, the transaction log is vital to Adaptive Server Anywhere replication systems and database recovery in event of system failures. When possible, it is recommended that the transaction log be placed on a physical device (in most cases, a disk drive) separate from the main database file, to reduce the chances of both the main database file and transaction log being affected in the event of a media failure. You can specify the name and location of the transaction log when you create the database.

This section shows you how to create databases at either the command prompt or in Interactive SQL. You can also create databases through Sybase Central, if you prefer, by opening the Utilities folder under Adaptive Server Anywhere 7.

4.2. Running a database server and starting databases

There are two versions of the database server installed on your machine. If you are just using Adaptive Server Anywhere locally, use the personal database server (dbeng7). If you are going to connect to the Adaptive Server Anywhere database over a network, however, you should use the network database server (dbsrv7). Examples in this document use dbeng7, but the two commands are, for the most part, interchangeable. See the table below for specific differences.

Syntax:

(dbeng7 | dbsrv7) [server-switches] [database-file [database-switches], ]

database-file specifies the path and filename to the database. You aren't actually required to specify a database file when you start up the database server, but if you don't, you must specify a name for the server using the -n switch. By default, if you do not specify a name for the database, it takes on the name of the database file, minus the path and extension. Similarly, if you do not specify a name for the database server (which you can do in server-switches), it takes on the name of the first database that was started on it.

For full details on the usage of dbeng7 and dbsrv7, see "The database server" in the Adaptive Server Anywhere Reference.

To start up the Adaptive Server Anywhere personal database server, but not a database, and name it MyServer, issue the following command at a prompt:

dbeng7 -n MyServer

To start up the Adaptive Server Anywhere personal database server and name it MyServer, then start a database on MyServer from mydb.db, naming it MyDatabase, issue the following command:

dbeng7 -n MyServer mydb.db -n MyDatabase

In the latter case, if you don't name the database server MyServer, it would be named MyDatabase instead.

There's a plethora of other switches available for the server. You can get a full listing of them by typing "dbeng7 -?" at a command prompt. A few important switches include the following:

• -c, for specifying Adaptive Server Anywhere's cache size

• -x allows you to specify the communications protocols

• -gt allows you to specify the number of processors to be used

• -ud tells the server to run as a daemon in UNIX (explained below)

4.3. Stopping the database server

Assuming you have the appropriate authority, you can stop the database server using any of the following methods:

• the dbstop command line utility

• using the STOP ENGINE SQL statement

• pressing the Q key when the server display window has the focus

NOTE: While the term engine is part of the SQL statement's name, server is the common term now used. This document will use the term server unless referring explicitly to the STOP ENGINE SQL statement.

By default, any user can stop a personal database server, but only a user with the DBA authority can stop a network database server. (This default can be changed by using the -gk switch when starting the server-see the Adaptive Server Anywhere Reference for details.)

The command line utility syntax is as follows:

dbstop [switches] {name}

If you are issuing dbstop to stop a locally-running server, you can simply specify the name of the database server in {name}. If the server is not running locally, you need to create a connection to the server before you can tell it to stop. The -c switch allows you to specify a connection string for the database running on the server that you would like to stop. To stop MyServer, execute the following command:

dbstop -c "uid=DBA;pwd=SQL;eng=MyServer;dbn=MyDatabase"

In this instance, you could also just give the server name, since the server is running locally:

dbstop MyServer

The first command connects to the database named MyDatabase on the server MyServer, then stops the server named MyServer. In the case that no databases are active on the server, you have to add "dbn=utility_db" to the connection string.

Let's say "Club" is the name of one of the databases running on a server named "Goliath," and you want to stop all the databases running on Goliath, including Club. The following command accomplishes that, as well as shutting down the database server:

dbstop -c "uid=DBA;pwd=SQL;eng=Goliath;dbn=Club"

If you have a database server named "David" running without any databases started on it, you can stop the server using the following command:

dbstop -c "uid=DBA;pwd=SQL;eng=David;dbn=utility_db"

The syntax for the STOP ENGINE statement is as follows:

STOP ENGINE [ server-name ] [ UNCONDITIONALLY ]

The server named server-name is stopped. If server-name is omitted, the currently running database server is stopped. If UNCONDITIONALLY is specified, the database server is stopped whether or not there are still connections to the server.

4.4. Stopping databases

It's also possible to stop individual databases without stopping the server, or any of the other databases that might be running on it. To do so, use the STOP DATABASE SQL statement.

Syntax:

STOP DATABASE database-name [ON engine-name] [UNCONDITIONALLY]

You specify the name of the database that you would like to stop in database-name, with the restriction that the database specified cannot be the currently connected one. The "ON engine-name" clause can be used only in Interactive SQL. You use it to specify the server that the database is running on. Outside of Interactive SQL, the database can only be stopped if it is on the current server. The UNCONDITIONALLY keyword forces databases to be stopped, even if there are connections to it. By default, you can't stop a database if there are connections active.

4.5. Connecting to a database

You can connect to an Adaptive Server Anywhere database via any of the following interfaces:

• ODBC

• OLE DB or ADO

• Embedded SQL

• Sybase Open Client

• JDBC

Regardless of how you connect, you must specify some parameters, such as a username and password, to establish a connection to the database. These can be specified in a connection string, the SQLCONNECT environment variable, an ODBC data source configuration, or the fields of a dialog box.

In this section, you'll find explanations on how to connect via SQL and ODBC.

As the Adaptive Server Anywhere network server is a client/server database, you may connect to a Linux-hosted database from Windows-based PCs and other non-Linux devices, as well as Linux applications. Programming interfaces such as OLE DB or ADO are available ony on Windows, but can still be used against a Linux-hosted database.

dbdsn [ modifier-switches ] 
 { -l 
 | -d dsn 
 | -g dsn 
 | -w dsn [details-switches] 
 | -cl                        }