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ContentsWhat Is Backup Server?Backup Server is an Open Server-based utility that handles all dumps and loads for SQL Server releases 10.0 and later. Backup Server provides flexible syntax for the dump and load commands and eliminates the need for the console program. Because it is a separate collection of processes, Backup Server does its tasks independently from the SQL Server, meaning that users experience much less performance degradation during dumps and loads.
How Does It Work?Backup Server runs on the same machine as SQL Server (or on the same cluster, for Digital OpenVMS). You can perform dumps and loads over the network by using two Backup Servers, one on the local machine and the other on a remote machine.When you dump database/transaction to dump devices known by a remote Backup Server (through sp_addumpdevice), the local Backup Server reads the database devices and sends the data over the network to the remote Backup Server, which stores it on the dump devices. When you use the load command, the local Backup Server sends instructions over the network to the remote Backup Server. The remote Backup Server reads the data from the dump devices and sends it back to the local Backup Server, which writes the data to the database devices. A network dump performs only as well as does the network supporting it, leading in many cases to significant performance decreases. Backup Server contains several major features to allow users to implement an unattended backup policy to improve dump and load performance. SQL Server is able to detect remaining space on database segments and allows automatic dumping and truncation of the transaction log when free space falls below particular thresholds. Backup Server:
Dump StripingBackup Server supports simultaneous dumps and loads with a maximum of 32 backup devices, in parallel, per dump or load. The number of simultaneous dumps and loads is limited by the system's configured maximum number of open files, and by shared memory resources. On Digital OpenVMS, that is the per- process limit. On UNIX, there is a limit on the number of processes per user ID, and a system-wide limit, since UNIX forks a separate process for each device to do the I/O. Refer to the System Administration Guide Supplement for your platform for more information on the maximum number of open files.See SYBASE SQL Server Utility Programs for UNIX for more information on the Backup Server's configurable parameters:
See "Developing a Backup and Recovery Plan" in the System Administration Guide for more information on the capabilities of the Backup Server.
ShutdownBackup Server supports immediate or deferred shutdown. You must connect to your SQL Server to issue the shutdown command to Backup Server.Deferred Shutdown The syntax for deferred shutdown is as follows:
1> shutdown backup_server_nameThis shutdown permits dumps and loads in progress to complete (including volume change notifications for these sessions), but will not permit initiation of new dumps and loads. When the last dump or load has completed, Backup Server disconnects and exits from all SQL Servers. Immediate Shutdown The syntax for immediate shutdown is as follows:
1> shutdown backup_server_name with nowaitThis causes Backup Server to drop all connections immediately and to exit.
What Is Required to Run Backup Server?Backup Server is an Open Server application and an independent process. As such, it uses memory and CPU resources, and acts like an independent SQL Server.
Name Entriessybinit inserts entries for Backup Server into the interfaces file and the sysservers table in the master database (where it is listed as "SYB_BACKUP"). If you have a remote Backup Server on another machine, put your interfaces file on a file server accessible to both machines, or else copy the remote Backup Server's entry from the remote interfaces file to the local one.The definition for the remote Backup Server must exist in the interfaces file on both the local and the remote system.
Additionally, if the Backup Server start-up option -S specifies a particular server name, all interfaces files must use that name, not another. In other words, you cannot use an alias for your Backup Server in the interfaces file as you can for other servers. For example:
Backup Server: 5.16.2.1: DB-Library error, error number 20011, severity 8: Backup Server: 5.16.2.1: DB-Library error, error number 20018, severity 5: UNIX Memory RequirementsUnder UNIX, Backup Server uses shared memory during dump and load (Digital OpenVMS does not use shared memory, so these calculations do not apply). The size and number of shared memory segments, and the number of process attachments to those segments, vary depending on the number of stripes and whether the dump is remote:
System Defaults The default number of shared memory segments a process can attach to varies from platform to platform. Refer to the System Administration Guide Supplement for your platform for this figure. If more than six stripes are to be dumped, the SHMSEG operating system configuration parameter needs to be increased. Because Digital OpenVMS has true asynchronous I/O built in, the Backup Server itself does all I/O and there is no sybmultbuf equivalent. There is no shared memory because there are no subprocesses ("child" processes) communicating with each other.
Tape Dump Device Configuration File (SQL Server release 11.0 and later)In SQL Server release 11.0 and later, sybinit prompts you for the name and location of a Backup Server configuration file during configuration of a Backup Server. The default name and location is:
$SYBASE/backup_tape.cfgWhen Backup Server encounters a dump device with which it is unfamiliar, it issues calls to the operating system in an attempt to get about the tape dump device. Backup Server writes this information to the configuration file for future use. The configuration file is a standard ASCII file.
Multi-File, Multi-Volume DumpsThe Backup Server allows writing of data from successive dumps to the same tape by default if the dump device type supports it. This feature makes efficient use of high-density archive media such as 8-mm tape.There are three main categories of devices:
SQL Server 10.x is more restrictive about supported devices. The following table summarizes hardware requirements for dump and load commands in SQL Server 10.x.
Tape Device Hardware Requirements in SQL Server 10.xThe following table lists device names and specific hardware requirements for dump/load to and from a tape device. The System Administration Guide Supplement for your platform may have further information. In the table below, N stands for the device number.
SQL Server 10.x requires non-rewinding devices so that Backup Server can control the positioning of the tape device.
Sun Solaris 2.xFor Sun Solaris 2.x environments, tape device names are constructed as follows:/dev/rmt/ unit_number density [BSD behavior] no rewind where density is "l" (low), "m" (medium), "h" (high), or "c" (compressed); and unit_number is a logical number that uniquely identifies the tape drive or unit. Tape device names indicating BSD behavior are used during installation, but should not be used with Backup Server.
Digital UNIXFor Digital UNIX environments, tape device names are constructed as follows:/dev/[n]nrmt/unit_number density where density is "a" or "l" (low), "m" (medium), or "h" (high); [n] indicates "no rewind"; and unit_number is a logical number that uniquely identifies the tape drive or unit.
Digital OpenVMSFor Digital OpenVMS environments, there is no standard device name for tape devices. Some typical names are: mua0, mub1, msa0. The devices are named as follows:type spec unit where:
HP-UXFor HP-UX environments, tape device names are constructed as follows:/dev/rmt/controller_number device number density [compression]no rewind where density is "l" (low), "m" (medium), or "h" (high).
Localization FilesBackup Server is an Open Server application, so it requires the $SYBASE/locales/locales.dat ([SYBASE.LOCALES]LOCALES.DAT on Digital OpenVMS) files that are required by Open Server, plus some additional files for each character set. Here is the list for the us_english, iso_1 character set:
locales/us_english/iso_1/bslib.loc Identical sets of files are located in each of the character set and language directories:
locales/us_english/cp437/Only U.S. English is provided with the basic product. If you have purchased one of the language modules, the same set of locales files is provided for each character set supported for the language. Following are the locations of files needed for some other languages:
Japaneselocales/japanese/deckanji/ Frenchlocales/french/cp437/ Germanlocales/german/cp437/Individual locales file names are the same for Digital OpenVMS, with paths like the following:
[SYBASE.LOCALES.US_ENGLISH.ISO_1]BSLIB.DOCAdditionally, Backup Server requires the file charset.loc in at least the default character set subdirectory (charsets/iso_1/charset.loc) and at least the default sort-order file (charsets/iso_1/roman8.srt for HP; charsets/iso_1/binary.srt for other platforms). By default, Backup Server uses the $SYBASE/locales/locales.dat file's entry for platform default as the locale. You can override this with the LANG shell variable or any of the Open Server language variables. With SQL Server release 10.0.1, you can use the backupserver command's -J option (the option is /character_set for Digital OpenVMS) to define the Backup Server's character set. See the backupserver entry in the SQL Server Utility Programs manual for your platform for more details.
Additional Requirements
Compatibility IssuesAn important goal of Sybase's dump/load architecture is to preserve compatibility with preceding releases. However, there are several dump and load compatibility issues to consider when moving from one SQL Server release level to another:
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