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关于jsp的一些好文章 主要介绍一些关于JSP的应用技巧方面的东西

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For tape media, BLOCKSIZE only applies if the tape is being overwritten by using FORMAT. When using tape <br>
media, the backup operation selects an appropriate block size. Explicitly stating a block size overrides <br>
the backup operation’s selection of a block size. <br>
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For PIPE, the backup operation uses 65,536 unless BLOCKSIZE is specified. <br>
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DESCRIPTION = {text | @text_variable} <br>
Specifies the free-form text describing the backup set. Can be a maximum of 255 characters. <br>
DIFFERENTIAL <br>
Specifies the database backup should consist only of the portions of the database that have changed since <br>
the last full backup. A differential database backup usually takes up less space than a full database. Use <br>
this option so that all individual log backups since the last full database backup do not need to be <br>
applied. For more information, see Differential Database Backups. <br>
The DIFFERENTIAL option is specified for full database backups only. <br>
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Note During a full database or differential backup, SQL Server backs up enough of the transaction log to <br>
produce a consistent database when the database is restored. <br>
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EXPIREDATE = {date | @date_var} <br>
Specifies the date when the backup set expires and can be overwritten. If supplied as a variable <br>
(@date_var), this date can be specified as either a string constant (@date_var = date), as a variable of <br>
character string data type (except for the ntext or text data types), a smalldatetime, or datetime <br>
variable, and it must follow the configured datetime format for the system. This option is used for disk <br>
and tape devices only and is effective only when specified with all backup sets on the media. <br>
RETAINDAYS = {days | @days_var} <br>
Specifies the number of days that must elapse before this backup media set can be overwritten. If supplied <br>
as a variable (@days_var), it must be specified as an integer. This option is used for disk and tape <br>
devices only and is effective only when specified with INIT. Specifying SKIP overrides this option. <br>
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Important If EXPIREDATE or RETAINDAYS is not specified, expiration is determined by the media retention <br>
configuration setting of sp_configure. These options only prevent SQL Server from overwriting a file. <br>
Tapes can still be erased using other methods, and disk files can still be deleted through the operating <br>
system. <br>
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FORMAT <br>
Specifies that the media header should be written on all volumes used for this backup operation and <br>
rewrites the backup device. Any existing media header is overwritten. The FORMAT option also invalidates <br>
the entire media contents, ignoring any existing password. <br>
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Important Use FORMAT carefully. Initializing one backup device or medium renders the entire backup set it <br>
contains unusable. For example, if a single tape belonging to an existing striped backup set is <br>
initialized, the entire backup set is rendered useless. <br>
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By specifying FORMAT, the backup operation implies SKIP and INIT; these do not need to be explicitly <br>
stated. <br>
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NOFORMAT <br>
Specifies the media header should not be written on all volumes used for this backup operation and does <br>
not rewrite the backup device unless INIT is specified. <br>
INIT <br>
Specifies the backup set should be the first file on the disk or tape device and preserves the media <br>
header. If INIT is specified, any existing data on that device is overwritten. <br>
The backup media is not overwritten if either of the following conditions is met: <br>
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All backup sets on the media have not yet expired. For more information, see the EXPIREDATE and RETAINDAYS <br>
options. <br>
The backup set name given in the BACKUP statement, if provided, does not match the name on the backup <br>
media. For more information, see the NAME clause. <br>
Use the SKIP clause to override these checks. For more information about interactions when using SKIP, <br>
NOSKIP, INIT, and NOINIT, see the Remarks section. <br>
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Note If the backup media is password-protected or encrypted, SQL Server does not write to the media. To <br>
overwrite media that is either password-protected or encrypted, specify the WITH FORMAT option. <br>
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NOINIT <br>
Specifies the backup set is appended to the current disk or tape device. NOINIT is the default. <br>
MEDIADESCRIPTION = {text | @text_variable} <br>
Specifies the free-form text description, maximum of 255 characters, of the media set. <br>
MEDIANAME = {media_name | @media_name_variable} <br>
Specifies the media name, a maximum of 128 characters, for the entire backup media set. If MEDIANAME is <br>
specified, it must match the previously specified media name already existing on the backup volume(s). If <br>
not specified or if the SKIP option is specified, there is no verification check of the media name. <br>
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Note If FORMAT is specified, MEDIANAME specifies the media name that is written. In addition, tapes shared <br>
between SQL Server database backups and Microsoft Windows NT&amp;reg; backups must have a nonnull MEDIANAME. <br>
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NAME = {backup_set_name | @backup_set_var} <br>
Specifies the name of the backup set. Names are limited to 128 characters. If NAME is not specified, it is <br>
blank. <br>
NOSKIP <br>
Instructs the BACKUP statement to check the expiration date and name of all backup sets on the media <br>
before allowing them to be overwritten. <br>
SKIP <br>
Disables the backup set expiration and name checking, which is usually performed by the BACKUP statement <br>
to prevent overwrites of backup sets. For more information, see the Remarks section. <br>
NOUNLOAD <br>
Specifies the tape is not unloaded automatically from the tape drive after a backup. NOUNLOAD remains set <br>
until UNLOAD is specified. This option is used only for tape devices. <br>
UNLOAD <br>
Specifies that the tape is automatically rewound and unloaded when the backup is finished. UNLOAD is set <br>
by default when a new user session is started. It remains set until that user specifies NOUNLOAD. This <br>
option is used only for tape devices. <br>
RESTART <br>
Specifies that SQL Server restarts the backup operation that was interrupted. The RESTART option saves <br>
time because it restarts the backup operation at the point it was interrupted. To RESTART a specific <br>
backup operation that was interrupted, repeat the entire BACKUP statement and add the RESTART option. <br>
Using the RESTART option is not required, but can save time. <br>
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Important This option can only be used for backups directed to tape media and for backups that span <br>
multiple tape volumes. A restart operation never occurs on the first volume of the backup. <br>
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STATS [ = percentage] <br>
Displays a message every time another percentage completes, and is used to gauge progress. If percentage <br>
is omitted, SQL Server displays a message after every 10 percent completed. <br>
&lt;file_or_filegroup&gt; <br>
Specifies the logical names of the files or filegroups to include in the database backup. Multiple files <br>
or filegroups may be specified. <br>
FILE = {logical_file_name | @logical_file_name_var} <br>
Names one or more files to include in the database backup. <br>
FILEGROUP = {logical_filegroup_name | @logical_filegroup_name_var} <br>
Names one or more filegroups to include in the database backup. <br>
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Note Back up a file when the database size and performance requirements make a full database backup <br>
impractical. To back up the transaction log separately, use BACKUP LOG. <br>
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Important To recover a database using file and filegroup backups, a separate backup of the transaction log <br>
must be provided by using BACKUP LOG. For more information about file backups, see Creating File or <br>
Filegroup Backups. <br>
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File and filegroup backups are disallowed if trunc. log on chkpt. is enabled for the database. If trunc. <br>
log on chkpt. is enabled, the log has been truncated and the log backups required to restore individual <br>
files and filegroups are not available. <br>
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The BACKUP statement requires that entire filegroups affected by a CREATE INDEX statement since the last <br>
filegroup backup be backed up as a unit: <br>
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If an index is created on a filegroup, that entire filegroup must be backed up in a single backup <br>
operation. Backups of individual files that are part of the affected filegroup are not allowed. <br>
If an index is created on a filegroup different from the one that the table resides in, then both <br>
filegroups (the filegroup containing the table and the filegroup containing the newly created index) must <br>
be backed up. If more than one index is created on a filegroup different from the filegroup in which the <br>
table resides, all filegroups must immediately be backed up to accommodate these differing filegroups. <br>
The BACKUP statement detects all of these filegroup situations and communicates to the backup user the <br>
minimum filegroups that must be backed up. <br>
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n <br>
Is a placeholder indicating that multiple files and filegroups may be specified. There is no maximum <br>
number of files or filegroups. <br>
LOG <br>
Specifies a backup of the transaction log only. The log is backed up from the last successfully executed <br>
LOG backup to the current end of the log. By default, SQL Server truncates the log up to the beginning of <br>
the active portion of the log, which contains the oldest open transaction. <br>
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Note If backing up the log does not appear to truncate most of the log, you may have a very old open <br>
transaction in the log. Log space can be monitored with DBCC SQLPERF (LOGSPACE). <br>
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NO_LOG | TRUNCATE_ONLY <br>
Removes the inactive part of the log without making a backup copy of it and truncates the log. This option <br>
frees space. Specifying a backup device is unnecessary because the log backup is not saved. NO_LOG and <br>
TRUNCATE_ONLY are synonyms. <br>
After backing up the log using either NO_LOG or TRUNCATE_ONLY, the changes recorded in the log are not <br>
recoverable. For recovery purposes, immediately execute BACKUP DATABASE. <br>
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If the log of a published (replicated) database becomes full and absolutely must be truncated, unsubscribe <br>
all subscriptions to the publications of that database. This allows you to truncate all distributed <br>
transactions. <br>
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NO_TRUNCATE <br>
Backs up the log without truncating it. This option also backs up the log if the database becomes damaged <br>
or if the database is marked suspect or has not been recovered. <br>
Remarks<br>
Database or log backups can be appended to any disk or tape device, allowing you to keep a database and <br>
its transaction logs all within one physical location. <br>
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SQL Server uses online backup to allow a database backup while the database is still in use. However, here <br>
are some operations that are not allowed during a database or transaction log backup: <br>
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File management operations such as the ALTER DATABASE statement with either the ADD FILE or REMOVE FILE <br>
options; INSERT, UPDATE, or DELETE statements are allowed during a backup operation. <br>
Shrink database or shrink file. This includes autoshrink operations. <br>
CREATE INDEX. This restriction applies to database backup, not log backup. <br>
Nonlogged operations such as bulk load, SELECT INTO, WRITETEXT, and UPDATETEXT. The database option select <br>
into/bulkcopy must be enabled for these operations to be nonlogged. <br>
If a backup is started when one of these operations is in progress, the backup ends. If a backup is <br>
running and one of these operations is attempted, the operation fails.<br>
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