Vchannel for Windows PC Archives

Vchannel for Windows PC Archives

Vchannel for Windows PC Archives

Vchannel for Windows PC Archives

5
RMAN Concepts I: Channels, Backups, and Copies

This chapter describes the basic concepts involved in using the Recovery Manager (RMAN) utility.

This chapter contains these topics:

RMAN Automatic and Manual Channel Allocation

This section contains these topics:

About RMAN Channels

An RMAN channel represents one stream of data to a device type and corresponds to one server session. Allocation of one or more RMAN channels is necessary to execute most backup and recovery commands. As illustrated in Figure 5-1, each channel establishes a connection from the RMAN executable to a target or auxiliary database instance by starting a server session on the instance. The server session performs the backup, restore, and recovery operations. Only one RMAN session communicates with the allocated server sessions.

Figure 5-1 Channel Allocation


Text description of the illustration sbr81083.gif

You can either allocate channels manually within a block, or preconfigure channels for use in all RMAN sessions using automatic channel allocation. RMAN comes preconfigured with a channel that you can use for backups and copies to disk. You can also run the command RMAN to specify automatic channels to disk or tape. In this way, you do not have to allocate channels every time you perform a backup, restore, or recovery operation.

When you run a command that requires a channel, and you do not allocate a channel manually, then RMAN automatically allocates the channels using the options specified in the command. For the command, RMAN allocates only a single type of channel, such as or . For the command and the various maintenance commands (for example, ), RMAN determines which device types are required, and allocates all necessary channels.

If you specify channels manually, then the command (executed only within a command) and command (executed only at the RMAN prompt) specify the type of I/O device that the server session will use to perform the backup, restore, or maintenance operation.

Whether the command or causes the media manager to allocate resources is vendor-specific. Some media managers allocate resources when you issue the command; others do not allocate resources until you open a file for reading or writing.

Automatic and Manual Channel Allocation

You can use the automatic channel allocation feature to configure a set of persistent, automatic channels for use in all RMAN sessions. You can use the manual channel allocation feature you to specify channels for commands used within a block.

Unless you manually run an command, RMAN allocates automatic channels according to the settings in these commands:

For example, you can issue the following commands at the RMAN prompt:

BACKUP DATAFILE 3; RUN { RESTORE TABLESPACE users; }

RMAN automatically allocates channels according to values set with the command in the following cases:

  • You use commands such as , , or outside of a block.
  • You use commands within a block but do not allocate any channels within the block.

You can override automatic channel allocation settings by manually allocating channels within a block. You cannot mix automatic and manual channels, so manual channels always override automatic channels. For example, you override automatic channel allocation when you issue a command as follows:

RUN { ALLOCATE CHANNEL c1 DEVICE TYPE sbt; BACKUP DATABASE PLUS ARCHIVELOG; }

RMAN optimizes automatic channel allocation by leaving automatic channels allocated so long as each new command requires exactly the same channel configuration as the previous command. For example, RMAN can use the same preallocated channels for the following series of commands:

BACKUP DATAFILE 1; BACKUP CURRENT CONTROLFILE; BACKUP ARCHIVELOG ALL;

If you issue a command such as or , then RMAN automatically releases the preallocated channels.

Automatic Channel Device Configuration

The command specifies the number of channels that RMAN uses when allocating automatic channels for a specified device type. For example, if you configure parallelism to 3, then RMAN allocates three channels of the default device type whenever it uses automatic channels.

When parallelizing, RMAN always allocates channels in numerical order, beginning with 1 and ending with the parallelism setting. For example, if the device type is and parallelization is set to 4, then RMAN allocates as follows:

ORA_SBT_TAPE_1 ORA_SBT_TAPE_2 ORA_SBT_TAPE_3 ORA_SBT_TAPE_4

You can change a parallelism setting by issuing another command. This example configures and then changes it to 3:

CONFIGURE DEVICE TYPE DISK PARALLELISM 2; CONFIGURE DEVICE TYPE DISK PARALLELISM 3;

The parallelism setting defines the number of channels for a device that RMAN allocates in parallel. It does not have to correspond to the actual number of channels configured for the device. For example, you can manually configure four different channels and set for to , , or .

You can view the default setting for parallelism by running the command. The default value is followed by a number sign (). For example:

RMAN> SHOW DEVICE TYPE; RMAN configuration parameters are: CONFIGURE DEVICE TYPE DISK PARALLELISM 1; # default

The following example configures the default device to and runs another command:

RMAN> CONFIGURE DEFAULT DEVICE TYPE TO sbt; new RMAN configuration parameters: CONFIGURE DEFAULT DEVICE TYPE TO 'sbt'; new RMAN configuration parameters are successfully stored RMAN> SHOW DEVICE TYPE; RMAN configuration parameters are: CONFIGURE DEVICE TYPE SBT PARALLELISM 1; # default CONFIGURE DEVICE TYPE DISK PARALLELISM 1; # default

Automatic Channel Default Device Types

Run the command to specify a default device type for automatic channels. For example, you may make backups to tape most of the time and only occasionally make a backup to disk. In this case, configure channels for disk and tape devices, but make the device of the default device:

CONFIGURE DEVICE TYPE DISK PARALLELISM 1; # configure device disk CONFIGURE DEVICE TYPE sbt PARALLELISM 2; # configure device sbt CONFIGURE DEFAULT DEVICE TYPE TO sbt;

RMAN only allocates channels when you run backup commands. For example, you may issue the following:

BACKUP TABLESPACE users;

RMAN only allocates channels of type during the backup because is the default device.

You can override the default device for backups and copies by specifying a different device on the command using the channel. For example, run a backup as follows:

BACKUP DEVICE TYPE sbt DATABASE;

If the default device type is , then the preceding command overrides this default and uses the channel configuration. Note that this command fails unless you have configured the device or configured channels.

During a restore operation, RMAN allocates all automatic channels according to the parallelism settings configured for each device type. The default device type configuration is irrelevant. For example, if you configure to for the default device and to for , then RMAN automatically allocates three channels and two channels during the restore.

Automatic Channel Naming Conventions

RMAN uses the following convention for channel naming: , where refers to the user's device type (such as or ) and refers to the channel number.


Note:

The and device types are synonymous, but RMAN output always displays whether the input is or .


For example, RMAN names the first channel , the second , and so forth. RMAN names the first channel , the second , and so forth. When you parallelize channels, RMAN always allocates channels in numerical order, starting with 1 and ending with the parallelism setting (), as in this example:

ORA_SBT_TAPE_1 ORA_SBT_TAPE_2 ORA_SBT_TAPE_3

Automatic channel allocation also applies to maintenance commands. If RMAN allocates an automatic maintenance channel, then it uses the same naming convention as any other automatically allocated channel. If you manually allocate a maintenance channel using , then RMAN uses the following convention for channel naming: , where refers to the user's device type (for example, or ) and refers to the channel number. For example, RMAN uses these names for two manually allocated disk channels:

ORA_MAINT_DISK_1 ORA_MAINT_DISK_2

Note that if you run the command to configure a device type and do not run for this device type, then RMAN allocates all channels without other channel control options. For example, assume that you configure the device and run a backup as follows:

CONFIGURE DEVICE TYPE sbt PARALLELISM 1; BACKUP DEVICE TYPE sbt DATABASE;

In effect, RMAN does the following:

RUN { ALLOCATE CHANNEL ORA_SBT_TAPE_1 DEVICE TYPE sbt; BACKUP DATABASE; }

Channel names beginning with the prefix are reserved by RMAN for its own use. You cannot manually allocate a channel with the command and then prefix the channel name with .

Automatic Channel Generic Configurations

The command configures generic settings that are used for all automatic channels of the specified device type. In other words, the command creates a template of settings that RMAN uses for all channels allocated on the device. For example, you can configure disk and tape channels as follows:

CONFIGURE CHANNEL DEVICE TYPE sbt PARMS='ENV=(NSR_SERVER=bksvr1)'; CONFIGURE CHANNEL DEVICE TYPE DISK RATE 5M FORMAT="?/oradata/%U" MAXOPENFILES=20;

Because you do not specify channel numbers for these channels, the channel settings are generic to all automatic channels of the specified type. The configuration acts as a template. For example, if you set for to , and the default device type is , then RMAN allocates ten disk channels using the settings in the command.

Automatic Channel Specific Configurations

You can also configure parameters that apply to one specific automatic channel. If you are running in an Oracle Real Application Clusters configuration or using a media manager that requires different settings on each channel, then you may find it useful to configure individual channels.

For example, in an Oracle Real Application Clusters environment you can enter:

CONFIGURE DEFAULT DEVICE DEVICE TYPE TO sbt; CONFIGURE DEVICE TYPE sbt PARALLELISM 2; CONFIGURE CHANNEL 1 DEVICE TYPE sbt CONNECT 'node1' PARMS='ENV=(NSR_SERVER=bksvr1)'; CONFIGURE CHANNEL 2 DEVICE TYPE sbt CONNECT 'node2' PARMS='ENV=(NSR_SERVER=bksvr1)';

In this example, RMAN allocates 2 channels for every backup job, and . The channel uses the settings for and the channel uses the settings for .

You can mix a command that creates a generic configuration with a command that creates a specific configuration. A generic automatic channel simply creates a configuration that can be used for any channel that is not explicitly configured. For example, assume that you run these commands:

CONFIGURE DEVICE TYPE DISK PARALLELISM 3; CONFIGURE CHANNEL DEVICE TYPE DISK MAXPIECESIZE = 2M; CONFIGURE CHANNEL 3 DEVICE TYPE DISK MAXPIECESIZE = 900K;

In this scenario, RMAN allocates and with option , using the settings for the channel with no number. RMAN allocates with because this channel was manually assigned a channel number. RMAN always allocates the number of channels specified in the parallelism parameter.

Clearing Automatic Channel Settings

You can specify the option for any command. The option returns the specified configuration to its default value. Assume you run these commands:

CONFIGURE DEVICE TYPE DISK CLEAR; # returns DISK to default parallelism CONFIGURE DEFAULT DEVICE TYPE CLEAR; # returns to default device type of DISK CONFIGURE CHANNEL DEVICE TYPE sbt CLEAR; # removes all the options for sbt channel CONFIGURE CHANNEL 3 DEVICE TYPE DISK CLEAR; # removes all configurations for 3rd channel

Each command removes the user-entered settings and returns the configuration to its default value. To see the default configuration settings, run the command before entering any configurations of your own. The defaults are prefixed with a number sign ().

Parallelization for Manually Allocated Channels

If you do not want to use automatic channels, then you can allocate multiple channels manually within a command, thus allowing a single RMAN command to read or write multiple backups or image copies in parallel. Thus, the number of channels that you allocate affects the degree of parallelism within a command. When backing up to tape you should allocate one channel for each physical device, but when backing up to disk you can allocate as many channels as necessary for maximum throughput.

Each manually allocated channel uses a separate connection to the target or auxiliary database. You can specify a different string for each channel to connect to different instances of the target database, which is useful in an Oracle Real Application Clusters configuration for distributing work across nodes.

RMAN internally handles parallelization of , , and commands. You only need to specify:

  • Multiple commands
  • The objects that you want to back up, copy, or restore

RMAN executes commands sequentially; that is, it completes the current command before starting the next one. Parallelism is exploited only within the context of a single command. Consequently, to create three backups of a datafile, issue a single command specifying all three datafiles rather than three separate commands.

The following script uses serialization to create the backups: three separate commands are used to back up one file each. Only one channel is active at any one time because only one file is being backed up.

RUN { ALLOCATE CHANNEL c1 DEVICE TYPE sbt; ALLOCATE CHANNEL c2 DEVICE TYPE sbt; ALLOCATE CHANNEL c3 DEVICE TYPE sbt; BACKUP DATAFILE 5; BACKUP DATAFILE 6; BACKUP DATAFILE 7; }

The following statement uses parallelization on the same example: one RMAN command backs up three datafiles, with all three channels in use. The three channels are concurrently active--each server session copies one of the datafiles to a separate tape drive.

RUN { ALLOCATE CHANNEL c1 DEVICE TYPE sbt; ALLOCATE CHANNEL c2 DEVICE TYPE sbt; ALLOCATE CHANNEL c3 DEVICE TYPE sbt; BACKUP DATAFILE 5,6,7; }

Channel Control Options for Manual and Automatic Channels

Whether you allocate channels manually or automatically, you can use channel control commands and options to do the following:

  • Control the operating system resources RMAN uses when performing RMAN operations
  • Affect the degree of parallelism for a backup or restore (in conjunction with the parameter of the command)
  • Set limits on I/O bandwidth consumption in kilobytes, megabytes, or gigabytes (, )
  • Set limits on the size of backup pieces (the parameter specified on the and commands)
  • Set limits on the size of backup sets (the parameter specified on the and commands)
  • Set limits on the number of concurrently open files (, )
  • Send vendor-specific commands to the media manager ()
  • Specify vendor-specific parameters for the media manager (, )
  • Specify which instance performs the operation (, )

On some platforms, the channel allocation and channel control commands specify the name or type of an I/O device to use. On other platforms, they specify which operating system access method or I/O driver to use. Not all platforms support the selection of I/O devices through this interface; on some platforms, I/O device selection is controlled through platform-specific mechanisms.

In Oracle9i, the command causes RMAN to contact the media manager whenever the type specified is other than . In releases before Oracle9i, the command does not cause RMAN to contact the media manager; RMAN does not call the media manager unless a , , or command is issued.


Note:

When you specify with any version of RMAN, RMAN does not allocate operating system resources other than for the creation of the server session and does not call the media manager.


Because RMAN has a preconfigured automatic channel, you do not have to manually allocate a maintenance channel when running , , or against a file that is only on disk (that is, an , , or ). A maintenance channel is useful only for a maintenance task; you cannot use it as an input or output channel for a backup or restore job.

Hardware Multiplexing by the Media Manager

Hardware multiplexing occurs when the media manager writes multiple RMAN backups to a single sequential device (such as a tape drive). Oracle Corporation does not recommend hardware multiplexing of RMAN backups.

Backup Sets

When you execute the command, you create one or more backup sets. This section contains these topics:

About Backup Sets

A backup set, which is a logical object, contains one or more physical backup pieces. By default, one backup set contains one backup piece. Backup pieces are operating system files that contain the backed up datafiles, control files, or archived redo logs. For example, you can back up ten datafiles into a single backup set containing a single backup piece (that is, a single output file). You cannot split a file across different backup sets or mix archived logs and datafiles into one backup set.

A backup set is a complete set of backup pieces that make up a full or incremental backup of the objects specified in the command. Backup sets are in an RMAN-specific format. An image copy, which is a complete image of a single datafile, control file, or archived log, is not in an RMAN-specific format.

You can back up datafiles, control files, archived redo logs, and the current server parameter file. You can also back up another backup set, as when you want to back up a disk backup to tape, or an image copy. For example, you can issue commands such as the following, each of which uses an automatic channel configuration:

BACKUP DATABASE; BACKUP TABLESPACE users, tools; BACKUP (SPFILE) (CURRENT CONTROL FILE); BACKUP BACKUPSET 12; BACKUP DATAFILECOPY '/tmp/system01.dbf';

When backing up datafiles, the target database must be mounted or open. If the database is in mode, then the target can be open or closed: you do not need to close the database cleanly. If the database is in mode, then you must close it cleanly before making a backup.


Note:

You cannot make a backup of a transported tablespace until after it has been specified read/write.


About Proxy Copies

A proxy copy is a special type of backup in which RMAN turns over control of the data transfer to a media manager that supports this feature. The option of the command specifies that a backup should be a proxy copy.

For each file that you attempt to back up using the command, RMAN queries the media manager to determine whether it can perform a proxy copy. If the media manager cannot proxy copy the file, then RMAN uses conventional backup sets to perform the backup. An exception occurs when you use the option, which causes Oracle to issue an error message when it cannot proxy copy.

Oracle records each proxy-copied file in the control file. RMAN uses this data to resynchronize the recovery catalog. Use the view to obtain the proxy copy information. Use the command or command to change the status of or delete a proxy backup.


Note:

The proxy functionality was introduced in Oracle8i Release 1 (8.1.5). If a proxy version of RMAN is used with a non-proxy target database, RMAN will not use proxy copy to create backup sets. If you make backups using proxy copy and then downgrade Oracle to a non-proxy version, RMAN will not use proxy copy backups when restoring and will issue a warning when the best available file is a proxy copy.


Storage of Backup Sets

RMAN can create backup sets that are written to disk or tertiary storage. If you specify , then you must back up to random access disks. You can make a backup on any device that can store an Oracle datafile: in other words, if the statement works, then is also a valid backup path name.

Using a media management system that is available and supported on your operating system, you can write backup sets to sequential output media such as magnetic tape. If you specify a device type such as that is other than , then you can back up to any media supported by the media management software.

Backup Set Compression

As Figure 5-2 illustrates, RMAN performs compression on its backups, which means that datafile blocks that have never been used are not backed up. Image copies of a datafile, however, always contain all datafile blocks.

Figure 5-2 Backup Set Compression


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Backups of Archived Logs

RMAN provides additional functionality for backups of archived redo logs. This section contains these topics:

Deletion of Archived Logs After Backups

Although you cannot archive logs directly to tape, you can use RMAN to back up archived logs from disk to tape. If you specify the option, then RMAN backs up exactly one copy of each specified log sequence number and then deletes the copy from disk after backing it up.

If you specify the option, then RMAN backs up exactly one copy of each specified log sequence number and then deletes the copies that match the specified criteria. For example, if you specify the parameter, RMAN deletes whichever logs match the string. RMAN automatically restores needed archived logs from tape to disk during recovery.

Backup Failover for Archived Redo Logs

In releases prior to Oracle9i, RMAN only looked in the first archiving destination for archived redo logs when backing them up. In Oracle9i, RMAN can perform archived redo log failover. RMAN can do the following:

  • If at least one log corresponding to a given log sequence and thread is available in any of the archiving destinations, then RMAN backs up the available log.
  • If there is a corrupt block in a log that RMAN is accessing, then RMAN searches other directories for a file without corrupt blocks.

RMAN always only backs up one copy of each distinct log sequence number. For example, assume that you archive logs 121 to 124 to two archiving destinations: and . The control file contains archived log records as follows:

SequenceFilename

121

121

122

122

123

123

124

124

However, unknown to RMAN, someone accidentally deletes logs 122 and 124 from the directory. Then, you run the following backup:

BACKUP ARCHIVELOG FROM SEQUENCE 121 UNTIL SEQUENCE 125;

In this case, RMAN can use the failover feature to back up the archived logs as described in the following table.

Sq.If RMAN Searches For . . .Then RMAN Can Find and Back Up . . .

121

122

(missing)

123

124

(missing)

Automatic Online Redo Log Switches During Backups of Archived Logs

At the beginning of every command that does not specify an clause, RMAN attempts to automatically switch out of and archive the current online redo log. In this way, RMAN can include the current redo log in the backup set.

If the database is open, then at the start of an archived log backup RMAN tries to switch out of and archive the current online log according to these rules:

  • RMAN runs .
  • If the clause or parameter is specified, RMAN does not try to switch or archive online logs.

Backups of Archived Logs Needing Backups

When making backups, run the command to archive online logs as well as back up archived logs. The purpose of this feature is to guarantee that the backed up datafiles can be recovered to a consistent state.

When is specified, RMAN performs the following actions in sequential order:

  1. Runs .
  2. Runs .
  3. Backs up the files specified in the command.
  4. Runs .
  5. Backs up any remaining archived redo logs generated during backup.

You cannot specify when explicitly backing up archived logs, but only when backing up another object such as the database. For example, you can run this command:

BACKUP DEVICE TYPE sbt DATABASE PLUS ARCHIVELOG;

Note:

If backup optimization is enabled, then RMAN skips backups of archived logs that have already been backed up to the allocated device.


Multiplexed Backup Sets

The technique of RMAN multiplexing is to simultaneously read files on disks and and then write them into the same backup piece. For example, RMAN can read from two datafiles simultaneously, and then combine the blocks from these datafiles into a single backup piece. Note that multiplexing in this sense is completely different from duplexing.

As Figure 5-3 illustrates, RMAN can back up three datafiles into a backup set that contains only one backup piece. This backup piece contains the intermingled data blocks of the three input files.

Figure 5-3 Datafile Multiplexing


Text description of the illustration sbr81053.gif

Multiplexing is affected by the factors described in Table 5-1.

Table 5-1 RMAN Multiplexing
ConceptsDefinition

Number of files in each backup set

The minimum of these values: setting, and the number of files read by each channel.

Multiplexing

The minimum of these values: setting, and the number of files in each backup set.

The parameter determines how many datafiles should be included in each backup set, while defines how many datafiles RMAN can read from simultaneously.

Assume that you are backing up six datafiles with one RMAN channel. If is and is , then the channel includes 6 datafiles in a set but does not multiplex the files because RMAN is not reading from more than one file simultaneously. The channel reads one file at a time and writes to the backup piece. In this case, the degree of multiplexing is 1.

Now, assume that is 6 and is . In this case, the channel can read and write in the following order:

  1. Read from datafiles , , and simultaneously and write to the backup piece
  2. Read from datafiles , and simultaneously and write to the backup piece

So in this example, the degree of multiplexing is 3 (the lesser of 6 and 3).

When multiplexing files, you can do the following:

  • Partition the datafiles into backup sets explicitly by assigning channels to specific datafiles, or let RMAN automatically select a partitioning.
  • Keep a high performance sequential output device streaming by including a sufficient number of datafiles in the backup. Keeping the device streaming is important for open database backups in which the backup operation must compete with the online system for I/O bandwidth.
  • Include the control file in a datafile backup set. In this case, the control file is written first and its blocks are not multiplexed with datafile blocks.
  • Create a backup set containing either datafiles or archived logs, but not both together. You cannot write datafiles and archived logs to the same backup set because the Oracle logical block size of the objects in a multiplexed backup must be the same.

Note that multiplexing too many files can decrease restore performance. If possible, group files that will be restored together into the same backup set. Assume that RMAN backs up seventeen files with = and = . You decide to restore , which is datafile 17. So, RMAN reads the multiplexed data for the first sixteen files and then starts reading the data for . In this case, moving to the beginning of the backup of may take more time than the restore itself.

Duplexed Backup Sets

RMAN provides an efficient way to produce multiple copies of each backup piece in a backup set. This functionality is also known as duplexing a backup set.

You can create up to four identical copies of each piece in a backup set by issuing one of the following commands, listed in order of precedence. If multiple commands are in effect simultaneously, then commands higher on the list override commands that are lower on the list.

CommandCommand RestrictionObject Restriction

Only command on which is specified

Any object specified on command

All commands within block

Any object specified on command

All commands

Only datafiles, control files, server parameter files, and archived logs


Note:

Control file autobackups on disk are a special case and are never duplexed: RMAN always writes one and only one copy.


You can specify up to 4 values for the option. RMAN uses the second, third, and fourth values only when , , or is specified. This example creates 3 copies of the backup of datafile :

BACKUP DEVICE TYPE DISK COPIES 3 DATAFILE 7 FORMAT '/tmp/%U','?/oradata/%U','?/%U';

RMAN places the first copy of each backup piece in , the second in , and the third in the Oracle home. Note that RMAN does not produce 3 backup sets, each with a different unique backup set key. Rather, RMAN produces one backup set with a unique key, and generates 3 identical copies of each backup piece in the set, as shown in this sample output:

List of Backup Sets =================== BS Key Type LV Size ------- ---- -- ---------- 1 Full 64K List of Datafiles in backup set 1 File LV Type Ckp SCN Ckp Time Name ---- -- ---- ---------- --------- ---- 7 Full 98410 08-FEB-02 /oracle/oradata/trgt/tools01.dbf Backup Set Copy #1 of backup set 1 Device Type Elapsed Time Completion Time Tag ----------- ------------ --------------- --- DISK 00:00:01 08-FEB-02 TAG20020208T152314 List of Backup Pieces for backup set 1 Copy #1 BP Key Pc# Status Piece Name ------- --- ----------- ---------- 1 1 AVAILABLE /tmp/01dg9tb2_1_1 Backup Set Copy #2 of backup set 1 Device Type Elapsed Time Completion Time Tag ----------- ------------ --------------- --- DISK 00:00:01 08-FEB-02 TAG20020208T152314 List of Backup Pieces for backup set 1 Copy #2 BP Key Pc# Status Piece Name ------- --- ----------- ---------- 2 1 AVAILABLE /oracle/oradata/01dg9tb2_1_2 Backup Set Copy #3 of backup set 1 Device Type Elapsed Time Completion Time Tag ----------- ------------ --------------- --- DISK 00:00:01 08-FEB-02 TAG20020208T152314 List of Backup Pieces for backup set 1 Copy #3 BP Key Pc# Status Piece Name ------- --- ----------- ---------- 3 1 AVAILABLE /oracle/01dg9tb2_1_3

When choosing which value to use for each backup piece, RMAN uses the first format value for copy number 1, the second format value for copy number 2, and so forth. If the number of format values exceeds the number of copies, then the extra formats are not used. If the number of format values is less than the number of copies, then RMAN reuses the format values, starting with the first one.

Parallelization of Backups

When you configure to greater than or manually allocate multiple channels, RMAN writes multiple backup sets in parallel. The server sessions divide the work of backing up the specified files.


Note:

You cannot stripe a backup set across multiple channels.


By default, RMAN determines which channels should back up which database files. You can use the command to manually assign a channel to back up specified files. You can also use the parameter to limit the number of datafiles included in a backup set. This example shows a parallelized backup to disk that uses the default automatic channels:

BACKUP (DATAFILE 1,2,3 FILESPERSET = 1 CHANNEL ORA_DISK_1) (DATAFILECOPY '/tmp/system01.dbf', '/tmp/tools01.dbf' FILESPERSET = 2 CHANNEL ORA_DISK_2) (ARCHIVELOG FROM SEQUENCE 100 UNTIL SEQUENCE 102 THREAD 1 FILESPERSET = 3 CHANNEL ORA_DISK_3);

You can also manually allocate channels as in the following example:

RUN { ALLOCATE CHANNEL c1 DEVICE TYPE sbt PARMS="ENV=(BACKUP_SERVER=tape_server1)"; ALLOCATE CHANNEL c2 DEVICE TYPE sbt PARMS="ENV=(BACKUP_SERVER=tape_server2)"; ALLOCATE CHANNEL c3 DEVICE TYPE sbt PARMS="ENV=(BACKUP_SERVER=tape_server3)"; BACKUP (DATAFILE 1,2,3 FILESPERSET = 1 CHANNEL c1) (DATAFILECOPY '/tmp/system01.dbf', '/tmp/tools01.dbf' FILESPERSET = 2 CHANNEL c2) (ARCHIVELOG FROM SEQUENCE 100 UNTIL SEQUENCE 102 THREAD 1 FILESPERSET = 3 CHANNEL c3); }

Figure 5-4 shows an example of parallelization in which channel backs up datafiles, channel backs up datafile copies, and channel backs up logs.

Figure 5-4 Parallelization of Backups


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Backups of Backup Sets

The RMAN command backs up backup sets rather than actual database files. This command supports disk-to-disk or disk-to-tape backups, but not tape-to-tape backups.

The command uses the default disk channel to copy backup sets from disk to disk. To back up from disk to tape, you must either manually allocate a channel of or configure an automatic channel.

Uses for Backups of Backup Sets

The command is a useful way to spread backups among multiple media. For example, you can execute the following command weekly as part of the production backup schedule:

BACKUP DEVICE TYPE sbt BACKUPSET ALL;

Note:

Backups to the device that use automatic channels require that you first run the command.


In this way, you ensure that all your backups exist on both disk and tape. Note that you can also duplex backups of backup sets (except for control file autobackups, which are never duplexed by ), as in this example:

BACKUP COPIES 2 DEVICE TYPE sbt BACKUPSET ALL;

You can also use to manage backup space allocation. For example, assume that you want more recent backups to exist on disk and older backups to exist on tape, but you do not need backups to exist on both disk and tape at the same time. In this case, you can regularly run the following command:

BACKUP BACKUPSET COMPLETED BEFORE 'SYSDATE-7' DELETE INPUT;

This command backs up backup sets that were created more than a week ago from disk to tape, and then deletes the backup sets from disk. Note that here is equivalent to : RMAN deletes all existing copies of the backup set. If you duplexed a backup to four locations, then RMAN deletes all four copies of the pieces in the backup set.

Backup Optimization When Backing Up Backup Sets

Note that if backup optimization is enabled when you issue the command to back up a backup set, and the identical backup set has already been backed up to the same device type, then RMAN skips the backup of that backup set. For example, the following command backs up to tape all backup sets that do not already exist on device type :

BACKUP DEVICE TYPE sbt BACKUPSET ALL;

Backup Failover When Backing Up Backup Sets

When backing up backup sets, RMAN searches for all available backup copies when the copy that it is trying to back up is either corrupted or missing. This behavior is similar to the behavior of RMAN when backing up archived redo logs that exist in multiple archiving destinations.

For example, assume that backup set 123 contains three backup pieces, and that was issued so that three copies of each backup piece exist. Each copy of a backup piece is on a different file system. The following table indicates that some of the copies of the pieces are corrupted or missing, while others are intact.

Backup Piece NumberCopy Number of the PieceStatus of Copy

1

1

Corrupted

1

2

Intact

1

3

Corrupted

2

1

Missing

2

2

Corrupted

2

3

Intact

3

1

Intact

3

2

Corrupted

3

3

Missing

Assume that you run the following command:

BACKUP BACKUPSET 123;

RMAN performs an automatic failover and includes only the uncorrupted copies in its backup set. The following table indicates which copies RMAN includes.

Backup Piece NumberCopy Number of the PieceStatus of Copy

1

2

Intact

2

3

Intact

3

1

Intact

Backup Options: Naming, Sizing, and Speed

Recovery Manager provides a number of options to control backups.

This section contains these topics:

Filenames for Backup Pieces

You can either let RMAN determine a unique name for backup pieces or use the parameter to specify a name. If you do not specify a filename, then RMAN uses the substitution variable to generate a unique name. For example, enter:

BACKUP TABLESPACE users;

RMAN automatically generates unique names for the backup pieces.

The parameter provides substitution variables that you can use to generate unique filenames. For example, you can run a command as follows:

BACKUP TABLESPACE users FORMAT = '/tmp/users_%u%p%c';

As described in "Duplexed Backup Sets", you can specify up to four values. RMAN uses the second, third, and fourth values only when you run , , or .


Note:

If you use a media manager, check your vendor documentation for restrictions on such as the size of the name, the naming conventions, and so forth.


Size of Backup Pieces

Each backup set contains at least one backup piece. If you do not restrict the backup piece size, then every backup set contains only one backup piece. To restrict the size of each backup piece, specify the option of the or commands. This option limits backup piece size to the specified number of bytes.

For example, restrict the backup piece size for disk backups to 2 GB by configuring an automatic disk channel, and then run a backup as follows:

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BlueStacks

American technology company known for its Android emulator
Private company
IndustryVirtualization, mobile software
GenreAndroidemulator
FoundedApril 25, 2009; 11 years ago (2009-04-25)[1][2][3]
FoundersRosen Sharma, Jay Vaishnav, Suman Saraf[4][3]
Headquarters,
Worldwide
  • Rosen Sharma
    (Chief executive officer, President)
  • Suman Saraf
    (Chief Technical Officer)
  • Hue Harguindeguy
    (Chief financial officer)
  • Jay Vaishnav
    (Founder & SVP of Products)
  • Ben Armstrong
    (VP of Business Development and Operations)
ProductsApp Player, GamePop
Websitewww.bluestacks.com

BlueStacks is an American technology company that produces the BlueStacks App Player and other cloud-based cross-platform products. The BlueStacks App Player is designed to enable Android applications to run on PCs running Microsoft Windows and Apple's macOS. The company was founded in 2009 by Jay Vaishnav, Suman Saraf, and Rosen Sharma, former CTO at McAfee and a board member of Cloud.com.

Investors include Andreessen Horowitz, Redpoint, Samsung, Intel, Qualcomm, Citrix, Radar Partners, Ignition Partners, AMD, and others.[8]

The company was announced May 25, 2011, at the Citrix Synergy conference in San Francisco. Citrix CEO Mark Templeton demonstrated an early version of BlueStacks onstage and announced that the companies had formed a partnership. The public alpha version of App Player was launched on October 11, 2011.[9] App Player exited beta on June 7, 2014.

App Player[edit]

The App Player can be downloaded on Windows and macOS software that virtualizes an Android OS. The software's basic features are free to download and use. Advanced optional features require a paid monthly subscription.[10] The company claims the App Player can run 1.5 million Android apps as of November 2019.[11] As of November 2019, BlueStacks have been downloaded over 210 million times.[12] App Player features mouse, keyboard, and external touchpad controls.

BlueStacks for Mac[edit]

On June 27, 2012, the company released an alpha-1 version of its App Player software for macOS,[13] while the beta version was released on December 27, 2012.

In April 2015, BlueStacks, Inc. announced that a new version of App Player for macOS, 2.0, was in development, which was released in July.[14]

BlueStacks 2[edit]

In December 2015, BlueStacks, Inc. released the new version BlueStacks 2.0[15] which lets users run multiple Android applications simultaneously.[16] BlueStacks 2.0 was also available for Mac OS X 10.9 Mavericks or later, till 2018.

BlueStacks TV (BTV)[edit]

On April 7, 2016, the company released BlueStacks TV which integrated Twitch.tv directly into the BlueStacks App Player.[17] This addition allows users to stream their apps to Twitch without the need for extra hardware or software. BlueStacks released Facebook Live integration in September 2016, allowing users to stream their gameplay to their Facebook profiles, Pages they control, or Facebook Groups they belong to.[18].

BlueStacks 3[edit]

In July 2017, BlueStacks released BlueStacks 3 based on a brand new engine and front-end design.[19] BlueStacks 3 added App Center which personalizes game suggestions, an account system, chat, new keymapping interface, and multi-instance. Multi-instance allows users to launch multiple BlueStacks windows using either the same or different Google Play account.

BlueStacks 3N[edit]

On January 19, 2018, BlueStacks announced the release of the BlueStacks + N Beta which runs on Android 7 (Android Nougat) and claimed to be the first and only Android gaming platform to have Android 7 at the time, since the majority of Android emulators ran Android 4.4 (KitKat), including prior BlueStacks versions.[20] This beta version is powered by an upgraded "HyperG" graphics engine allowing BlueStacks to utilize the full array of Android 7 APIs

BlueStacks 4[edit]

On September 18, 2018, BlueStacks announced the release of its latest flagship version, BlueStacks 4. BlueStacks 4 benchmarks 6-8x faster than every major mobile phone according to the Antutu benchmark.[21] BlueStacks 4 also includes dynamic resource management which only initializes the required Android libraries thus freeing resources. A new dock and search offer a clean user interface. New AI powered key-mapping tool auto maps keys in supported games with key customization also available for further tweaking. In addition, BlueStacks 4 supports[22] both 32-bit and 64-bit version of Android 7.1.2 Nougat.

Development for macOS has been restarted, and version 4 is currently available from the website as of November 2019, first released for Mac in January 2019.[23]

BlueStacks 4 64-Bit Beta[edit]

On January 17, 2019, BlueStacks released a 64-bit version of BlueStacks 4 via its early access program.[24] This version runs on a 64-bit version of Android 7.1.2 which allows for improved performance, and more efficient memory usage. The prerequisites for running this build include running a 64-bit version of Windows 8 or later, with virtualization enabled, and Hyper-V disabled. This 64-bit release allows the installation and usage of ARM64-v8a android applications.

Minimum requirements[edit]

Current minimum requirements for App Player for Windows include: Windows 7 or higher, 2 GB or higher system memory, 5 GB of hard drive space, administrator rights, and an Intel or AMD processor.[6] BlueStacks clashes with the BitDefender antivirus software.[25] An update to the latest graphic card driver version is also recommended.

Minimum requirements for macOS are: macOS Sierra or higher, 4 GB RAM, 4 GB disk space.

GamePop[edit]

On May 9, 2013, the subscription service GamePop was announced.[26] It allows users to play as many as 500 mobile games on TV. On July 23, 2014 Samsung announced [8] it had invested in and was backing GamePop. This brought total outside investment in BlueStacks to $26 million.[27]

See also[edit]

References[edit]

  1. ^"BlueStacks hits a billion apps used per month and launches new mobile platform". VentureBeat. December 3, 2015. Archived from the original on June 9, 2020. Retrieved June 9, 2020.
  2. ^"BlueStacks Partners With AMD, Bringing 500,000 Android Apps To Windows PCs". TechCrunch. Retrieved June 9, 2020.
  3. ^ ab"Bluestacks". CrunchBase. Archived from the original on June 9, 2020.
  4. ^Media, Ryan Daws | 19th September 2018 | TechForge (September 19, 2018). "BlueStacks emulates Android '6x faster' than leading smartphone and is a verified app (safe to download)". Developer Tech News. Archived from the original on June 9, 2020. Retrieved June 9, 2020.
  5. ^"Download BlueStacks Offline Installer". Bluestacks - The Best Android Emulator on PC as Rated by You. January 21, 2017. Archived from the original on October 8, 2018. Retrieved November 2, 2019.
  6. ^ ab"System requirements for BlueStacks 4". BlueStacks Support. Archived from the original on November 2, 2019. Retrieved November 2, 2019.
  7. ^"How can I Install and launch BlueStacks on Mac OS?". BlueStacks Support. Archived from the original on November 2, 2019. Retrieved November 2, 2019.
  8. ^ abEtherington, Darrell. "After 10M Downloads, Samsung Backs GamePop As BlueStacks Adds $13M In New Funding". TechCrunch. Archived from the original on July 24, 2014. Retrieved July 23, 2014.
  9. ^Empson, Rip. "BlueStacks Releases App Player And Cloud Connect Service To Let You Run Android Apps On Your PC". TechCrunch. Archived from the original on December 8, 2011. Retrieved December 4, 2011.
  10. ^Whitney, Lance. "Android apps can now run on your PC via BlueStacks". CNET. Archived from the original on December 8, 2011. Retrieved December 4, 2011.
  11. ^"BlueStacks Features and Comparison". Bluestacks - The Best Android Emulator on PC as Rated by You. Archived from the original on November 2, 2019. Retrieved November 2, 2019.
  12. ^"What is Bluestacks?". Bluestacks - The Best Android Emulator on PC as Rated by You. Archived from the original on November 1, 2019. Retrieved November 2, 2019.
  13. ^Rosenblatt, Seth. "BlueStacks ports Android apps to Mac". CNET. Archived from the original on June 28, 2012. Retrieved July 28, 2012.
  14. ^"BlueStacks - Did you pre-order the new Macbook?". www.facebook.com. Retrieved November 2, 2019.
  15. ^"Bluestacks Review and Fix Engine issues". TechnoIliyas. Archived from the original on May 13, 2020. Retrieved March 31, 2020.
  16. ^"BlueStacks 2.0 Launched, Lets You Run Multiple Apps Simultaneously". NDTV Gadgets 360. Archived from the original on November 2, 2019. Retrieved November 2, 2019.
  17. ^"Twitch users can now live stream Android games from their PC". techcrunch.com. Archived from the original on April 8, 2016. Retrieved April 7, 2016.
  18. ^"Stream Android apps on Facebook Live with Bluestacks". engadget.com. Archived from the original on September 22, 2016. Retrieved September 22, 2016.
  19. ^"BlueStacks 2 vs. BlueStacks 3 Features". bluestacks.com. July 30, 2017. Archived from the original on July 30, 2017. Retrieved November 2, 2019.
  20. ^"Android N Comes to PC; BlueStacks Releases the First Android Gaming Platform Ever to Run Android N". gamasutra.com. Archived from the original on January 19, 2018. Retrieved January 19, 2018.
  21. ^"BlueStacks, an Android emulator for PC, gets an update with major performance upgrade". gamasutra.com. Archived from the original on September 19, 2018. Retrieved January 19, 2018.
  22. ^Kumar, Rahul (August 19, 2019). "Is Bluestacks safe for Windows and macOS PC?". HubsAdda. Archived from the original on August 19, 2019. Retrieved August 19, 2019.
  23. ^"Release Notes". BlueStacks Support. Archived from the original on November 4, 2019. Retrieved November 4, 2019.
  24. ^"Join our Discord Server for Early Access Releases and a Great Community". reddit.com. Retrieved March 15, 2019.
  25. ^"r/BlueStacks - BlueStack and Bitdefender blocking some XML files". reddit. Retrieved November 2, 2019.
  26. ^Empson, Rip. "After 10M Downloads, BlueStacks Takes On OUYA With Game Console And $6.99 All-You-Can-Play Service". TechCrunch. Archived from the original on June 7, 2013. Retrieved June 11, 2013.
  27. ^"Samsung invests $13M in Android microgaming console GamePop". CNET. Archived from the original on March 7, 2018. Retrieved June 13, 2017.

External links[edit]

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