rman的backup命令中format使用的替换变量的含义

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formatSpec
The following table lists RMAN substitution variables that are valid in format strings.
Syntax Element Description
%a Specifies the activation ID of the database.
%b Specifies the file name stripped of directory paths. It is only valid for SET NEWNAME and backup when producing image copies It will yield errors if used as a format specification for a backup that produces backup pieces.
%c Specifies the copy number of the backup piece within a set of duplexed backup pieces. If you did not duplex a backup, then this variable is 1 for backup sets and 0 for proxy copies. If one of these commands is enabled, then the variable shows the copy number. The maximum value for %c is 256.
%d Specifies the name of the database (see Example 4-22).
%D Specifies the current day of the month from the Gregorian calendar in format DD.
%e Specifies the archived log sequence number.
%f Specifies the absolute file number (see Example 4-22).
%F Combines the DBID, day, month, year, and sequence into a unique and repeatable generated name. This variable translates into c-IIIIIIIIII-YYYYMMDD-QQ, where:
IIIIIIIIII stands for the DBID. The DBID is printed in decimal so that it can be easily associated with the target database.
YYYYMMDD is a time stamp in the Gregorian calendar of the day the backup is generated
QQ is the sequence in hexadecimal number that starts with 00 and has a maximum of 'FF' (256)

%h Specifies the archived redo log thread number.
%I Specifies the DBID.
%M Specifies the month in the Gregorian calendar in format MM.
%N Specifies the tablespace name. This substitution variable is only valid when backing up datafiles as image copies.
%n Specifies the name of the database, padded on the right with x characters to a total length of eight characters. For example, if prod1 is the database name, then the padded name is prod1xxx.
%p Specifies the piece number within the backup set. This value starts at 1 for each backup set and is incremented by 1 as each backup piece is created.
Note: If you specify PROXY, then the %p variable must be included in the FORMAT string either explicitly or implicitly within %U.

%s Specifies the backup set number. This number is a counter in the control file that is incremented for each backup set. The counter value starts at 1 and is unique for the lifetime of the control file. If you restore a backup control file, then duplicate values can result. Also, CREATE CONTROLFILE initializes the counter back to 1.
%t Specifies the backup set time stamp, which is a 4-byte value derived as the number of seconds elapsed since a fixed reference time. The combination of %s and %t can be used to form a unique name for the backup set.
%T Specifies the year, month, and day in the Gregorian calendar in this format: YYYYMMDD.
%u Specifies an 8-character name constituted by compressed representations of the backup set or image copy number and the time the backup set or image copy was created.
%U Specifies a system-generated unique filename (default).
The meaning of %U is different for image copies and backup pieces. For a backup piece, %U specifies a convenient shorthand for %u_%p_%c that guarantees uniqueness in generated backup filenames. For an image copy of a datafile, %U means the following:
data-D-%d_id-%I_TS-%N_FNO-%f_%u
For an image copy of an archived redo log, %U means the following:
arch-D_%d-id-%I_S-%e_T-%h_A-%a_%u
For an image copy of a control file, %U means the following:
cf-D_%d-id-%I_%u

%Y Specifies the year in this format: YYYY.
%% Specifies the percent (%) character. For example, %%Y translates to the string %Y.