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DBCC SHRINKLOG - Analytics Platform System (PDW)

  • Artikkeli

Applies to: Analytics Platform System (PDW)

Reduces the size of the transaction log across the appliance for the current Analytics Platform System (PDW) database. The data is defragmented in order to shrink the transaction log. Over time, the database transaction log can become fragmented and inefficient. Use DBCC SHRINKLOG to reduce fragmentation and reduce the log size.

Transact-SQL syntax conventions

Syntax

DBCC SHRINKLOG
    [ ( SIZE = { target_size [ MB | GB | TB ]  } | DEFAULT ) ]
    [ WITH NO_INFOMSGS ]
[;]

Arguments

SIZE = { target_size [ MB | GB | TB ] } | DEFAULT

target_size is the desired size for the transaction log, across all the Compute nodes, after DBCC SHRINKLOG completes. It is an integer greater than zero.

The log size is measured in megabytes (MB), gigabytes (GB), or terabytes (TB). It is the combined size of the transaction log on all of the Compute nodes.

By default, DBCC SHRINKLOG reduces the transaction log to the log size stored in the metadata for the database. The LOG_SIZE parameter in CREATE DATABASE (Azure Synapse Analytics) or ALTER DATABASE (Azure Synapse Analytics) determines the log size in the metadata. DBCC SHRINKLOG reduces the transaction log size to the default size when SIZE = DEFAULT is specified, or when the SIZE clause is omitted.

WITH NO_INFOMSGS

Informational messages are not displayed in the DBCC SHRINKLOG results.

Permissions

Requires ALTER SERVER STATE permission.

Remarks

DBCC SHRINKLOG does not change the log size stored in the metadata for the database. The metadata continues to contain the LOG_SIZE parameter that was specified in CREATE DATABASE or ALTER DATABASE statement.

Examples

A. Shrink the transaction log to the original size specified by CREATE DATABASE

Suppose the transaction log for the Addresses database was set to 100 MB when the Addresses database was created. That is, the CREATE DATABASE statement for Addresses had LOG_SIZE = 100 MB. Now, suppose the log grows to 150 MB and you want to shrink it back to 100 MB.

Each of the following statements attempt to shrink the transaction log for the Addresses database to the default size of 100 MB. If shrinking the log to 100 MB will cause data loss, DBCC SHRINKLOG shrinks the log to the smallest size possible, greater than 100 MB, without losing data.

USE Addresses;
GO
DBCC SHRINKLOG ( SIZE = 100 MB );
GO
DBCC SHRINKLOG ( SIZE = DEFAULT );
GO
DBCC SHRINKLOG;
GO

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