Backup and Recovery Properties#

These properties are related to the management of change logs, which are maintained in response to database changes.

ARCHIVE_DIR#

Data Type#

String

Default Value#

$ALTIBASE_HOME/arch_logs

Attributes#

Read-Only, Multiple Values

Range#

None

Description#

This property specifies the directory or directories in which to store archive log files when performing an archive log backup. If this value is not expressly specified by the user, the default location is $ALTIBASE_HOME/arch_logs.

The number of directories specified in this property must be the same as the number specified in the LOG_DIR property.

The user can explicitly specify the value(s), but the specified directories must be created first. If not, an error message will be output, and Altibase will not start.

ARCHIVE_FULL_ACTION#

Data Type#

Unsigned Integer

Default Value#

0

Attributes#

Read-Only, Single Value

Range#

[0, 1]

Description#

This property controls the action of the archivelog thread, which conducts archive log backup, when there is not enough disk space in the archive log destination (specified using ARCHIVE_DIR).

If this parameter is set to 0, the archivelog thread will output an error message and stop the archive log file backup. Even if enough disk space can subsequently be secured, archive log backup will not resume until the user explicitly issues a command to do so. If checkpointing takes place in such cases, unnecessary log files will be deleted, even if no archive log file backup has been conducted. Therefore care must be taken when using this mode.

If this parameter is set to 1, the archivelog thread waits until enough disk space can be secured to perform the archive log file backup. Because the archive log files have not been backed up, care must be taken to prevent the log files from being deleted if checkpointing takes place during this waiting period.

ARCHIVE_MULTIPLEX_COUNT#

Data Type#

Unsigned Integer

Default Value#

0

Attributes#

Read-Only, Single Value

Range#

[0, 10]

Description#

This property specifies how many copies of the archive log file¹ are to be kept by the Altibase server. After this property has been specified, copies of newly archived log files are kept.

The ARCHIVE_MULTIPLEX_COUNT and ARCHIVE_MULTIPLEX_DIR properties can be specified while the server is shutdown.

ARCHIVE_MULTIPLEX_DIR#

Data Type#

String

Default Value#

""

Attributes#

Read-Only, Multiple Value

Range#

None

Description#

This property specifies the path for copies of the archive log file. The number of values specified in the ARCHIVE_MULTIPLEX_DIR properties must be equal to the value specified in the ARCHIVE_MULTIPLEX_COUNT property. It is recommended to set each path to a separate disk.

ARCHIVE_THREAD_AUTOSTART#

Data Type#

Unsigned Integer

Default Value#

1

Attributes#

Read-Only, Single Value

Range#

[0, 1]

Description#

This property specifies whether to activate the archivelog thread, which periodically performs archive log file backups. If this property is 1, the archivelog thread is activated.

After the archivelog thread has been suspended due to insufficient disk space in the backup directory, this property is used to restart the thread automatically after sufficient disk space is secured.

CHECKPOINT_ENABLED#

Data Type#

Unsigned Integer

Default Value#

1

Attributes#

Read-Only, Single Value

Range#

[0, 1]

Description#

This property specifies whether checkpointing is enabled ("ON") or disabled ("OFF").

0: OFF

1: ON

When this value is 0 ("OFF"), the checkpoint thread cannot be started, and additionally it cannot operate the checkpoint interval specified by CHECKPOINT_INTERVAL_IN_SEC and CHECKPOINT_INTERVAL_IN_LOG. However, the user can perform checkpointing manually.

CHECKPOINT_INTERVAL_IN_LOG#

Data Type#

Unsigned Integer

Default Value#

10

Attributes#

Read-Write, Single Value

Range#

[1, 2³²-1]

Description#

This property defines the checkpoint interval based on the log file creation count. In other words, after the log files have been replaced the number of times specified using this property, checkpointing will be automatically executed. When checkpointing is requested based on this property, it may be impossible to execute, either because checkpointing is already underway, or for some other reason.

In such cases, checkpointing is not initiated immediately again after the checkpointing that is already underway has finished; instead, the current checkpointing request is canceled. Therefore, the next checkpointing request will occur when the number of log files reaches the value set in this property.

This property can be changed using the ALTER SYSTEM statement while Altibase is running.

CHECKPOINT_INTERVAL_IN_SEC (Unit: second)#

Data Type#

Unsigned Integer

Default Value#

6000

Attributes#

Read-Write, Single Value

Range#

[3, 2592000]

Description#

This property specifies the checkpoint interval in seconds.

This property can be changed using the ALTER SYSTEM statement while Altibase is running.

COMMIT_WRITE_WAIT_MODE#

Data Type#

Unsigned Integer

Default Value#

0

Attributes#

Read-Write, Single Value

Range#

[0, 1]

Description#

This property specifies whether to wait until logs have been written to log files when committing transactions. In Altibase, the default is not to wait, in the interests of better performance.

This property can be set for the entire system or for individual user sessions, and thus this property can be changed using either the ALTER SYSTEM or ALTER SESSION statement while Altibase is running.

0: Do Not Wait

1: Wait

INCREMENTAL_BACKUP_CHUNK_SIZE#

Data Type#

Unsigned Integer

Default Value#

4

Attributes#

Read-Only, Multiple Value

Range#

[0, 2³²-1]

Description#

This property is specified to track the changes made to pages of data(unit: pages). For example, if the value of this property is set to 4, change tracking information is recorded for every 4 pages and all of the 4 pages are backed up if one of the 4 pages is changed.

To alter the value of this property, the changeTracking file must be recreated in the following steps:

1: Shut down the server and then alter the value in the properties file.
2: Start up the server.
3: Disable change tracking and then reactivate it.

INCREMENTAL_BACKUP_INFO_RETENTION_PERIOD#

Data Type#

Unsigned Integer

Default Value#

0

Attributes#

Read-Only, Single Value

Range#

[0, 2³²-1]

Description#

This property specifies the period of time(unit: days) during which backup information stored in the backupInfo file is retained

Backup information deleted with the ALTER DATABASE DELETE OBSOLETE BACKUP FILES statement ranges from the oldest expired level 0 backup to the level 1 backup immediately prior to the oldest unexpired level 0 backup.

Note: Backup files backed up at level 0 are a prerequisite for incremental backups. Regardless of the existence of backup information which has expired the maintenance period specified for this property and the corresponding backup files, if only a level 0 backup has been performed, expired backup information and backup files are not deleted, even if the "ALTER DATABASE DELETE OBSOLETE ..." statement is executed.

LOG_BUFFER_TYPE#

Data Type#

Unsigned Integer

Default Value#

0

Attributes#

Read-Only, Single Value

Range#

[0, 1]

Description#

This property determines the log buffer type. If it is set to 0, the OS kernel log buffer is used. If it is set to 1, the process memory log buffer is used.

This property cannot be changed while the system is running.

LOG_MULTIPLEX_COUNT#

Data Type#

Unsigned Integer

Default Value#

0

Attributes#

Read-Only, Single Value

Range#

[0, 10]

Description#

This property specifies how many copies of the log file² are to be kept by the Altibase server. Whenever original log files are created or dropped, the copies of log files are also simultaneously created or dropped.

The LOG_MULTIPLEX_COUNT and LOG_MULTIPLEX_DIR properties can be specified while the server is shutdown.

LOG_MULTIPLEX_DIR#

Data Type#

String

Default Value#

""

Attributes#

Read-Only, Single Value

Range#

None

Description#

This property specifies the path for copies of the log file. The number of values specified in the LOG_MULTIPLEX_DIR properties must be equal to the value of the LOG_MULTIPLEX_COUNT property. It is recommended to set each path to a separate disk.

PREPARE_LOG_FILE_COUNT#

Data Type#

Unsigned Integer

Default Value#

5

Attributes#

Read-Only, Single Value

Range#

[0, 2³²-1]

Description#

If there is not enough space in the log file when logs are written, a new log file is created, which can increase the transaction response time. To prevent such delays in transaction execution caused by the creation of log files, Altibase creates extra log files ("prepare log files") in advance. This parameter specifies the number of such log files.

SNAPSHOT_MEM_THRESHOLD (Unit: percentage)#

Data Type#

Unsigned Integer

Default Value#

80

Attributes#

Read-Write, Single Value

Range#

[0, 100]

Description#

This is a property which sets up available thresholds for use in memory database after the snapshot settings (BEGIN SNAPSHOT).

The percentage of the MEM_MAX_DB_SIZE property which is currently being used by memory is verified, and if it exceeds the specified threshold, the snapshot is automatically stopped.

SNAPSHOT_DISK_UNDO_THRESHOLD (Unit: percentage)#

Data Type#

Unsigned Integer

Default Value#

80

Attributes#

Read-Write, Single Value

Range#

[0, 100]

Description#

This property specifies thresholds usable in disk after the snapshot settings (BEGIN SNAPSHOT).

It verifies what percentage of the SYS_UNDO_FILE_MAX_SIZE property has been used by the disk undo tablespace up to now, and if it exceeds specified threshold, the snapshot is automatically stopped.

Multiplexing archive log files: This feature copies the archive log files to a separate disk to prepare for the event of damage to the original archive log files. ↩
Multiplexing Log Files: This feature copies the log files to which all changes of the database have been written, to a separate disk to prepare for the event of damage to the original log files. ↩