Relationship between the CHANNEL parameters PARALLELISM and FILESPERSET in RMAN Configuration

In RMAN configuration, the relationship between the CHANNEL-related parameters PARALLELISM and FILESPERSET is PARALLELISM --- www.2cto.com. We can also use the parallelism parameter to specify how many channels are automatically created at the same time: RMAN> configure device type disk parallelism 3; indicates that three channels are enabled to speed up Backup recovery. By default, the degree of PARALLELISM of the automatically allocated channel is 1. If you set the parallel channel to 2 by setting PARALLELISM, In the run block, if you do not specify a CHANNEL through the allocate channel command, two parallel channels are used by default. If you specify several ALLOCATE channels in the run Command block, then, when running the BACKUP command, rman will take the channel you set as the standard, regardless of the number of parallel channels configured in configure. Note that the backup command has a FILESPERSET parameter, which is the maximum number of data files that can be contained in each backup set created by rman. (Note: the default value of this parameter is 64. If this parameter is not specified when the backup command is executed, then rman will only use the first channel for backup, and other channels will be idle. There is also a size relationship between the number of channels and the FILESPERSET value, and the logic is slightly complicated. For example, if the number of datafiles is 25 and FILESPERSET is 8, four backupsets (25/8 = 3.125) are generated during database backup. Each backup set contains eight data files. ----- Define the number of channels in parallel and channel attributes. Allocate channel provides backup concurrency. If the average number of files <filesperset, backup is performed based on the average number of files/backup sets. If the number of files exceeds the limit, backup sets are generated based on the number of filesperset. For example: 1. run {allocate channel partition type disk; allocate channel ch2 type disk; backup datafile, filesperset 3; release channel partition; release channel ch2;} the average is 4 (number of files) /2 (number of channels) = 2, less than filesperset 3, two backup sets are generated. Each backup set contains two data files. 2. run {allocate channel category type disk; allocate channel ch2 type disk; backup dataf Ile 3, 4, 5, 6 filesperset 1; release channel success; release channel ch2;} generates four backup sets, each containing a data file Example 1: RMAN> configure device type disk parallelism 4; RMAN> configure channel 1 device type disk; RMAN> configure channel 2 device type disk; note: In the preceding configuration, four channels are enabled, and user configurations are used for channel 1 and 2, 3, 4 Adopts the default configuration. Example 2: RMAN> configure device type disk parallelism 3; RMAN> configure channel 1 device type disk; RMAN> configure channel 2 device type disk; RMAN> configure channel 3 device type disk; RMAN> configure channel 4 device type disk. Note: At this time, RMAN ignores the settings of parallelism, and the channels set by the user prevail. Www.2cto.com: How Does oracle choose between filesperset and channel? Let's take a look at how our experts say ----------------------------------------------- -- biti_rainy filesperset = files per backupset has 10 datafiles, filesperset = 4 10/4 = 2.5 when you back up the database, generate three backupsets -------------------------- -- piner filesperset indicates that each backup set can back up to several data files or archive logs. One backup set can have multiple backups. data files and other backups cannot span the backup set, but can span the backup set. Therefore, it is correct that the backup set contains a certain data file... -- Added by blog Author: Note: maxpiecesize is used to set the size of the backup part. For example, if the maximum size of a backup slice is 2000 MB, a 5 GB data file must be backed up across the backup slice, but one data file cannot be backed up across multiple backup sets. A channel usually corresponds to a backup set. Configure channel device type 'sbt _ TAPE 'MAXPIECESIZE 2000 M; ------------------- -- husthxd use filesperset to control the size of the Backup set. When the filesperset parameter is specified, rman compares filesperset with automatically calculated values (number of files in each allocated channel) and takes a smaller value to ensure that all channels are used. If the number of files specified or indicated by the combination of backupSpec statements is greater than that of filesperset, rman creates multiple backup sets to maintain the correct rate (ratio). If filesperset is not specified, rman compares the calculated values (number of files divided by the allocated channel) with the default value 64, and takes a smaller value to ensure that all channels are available. Rman usually tries to create enough backup sets so that all allocated channels have something to do. One exception is that there are more channels than files to be backed up.