VT_SYSTEM monitors the overall state of the database.
Column Name
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Description
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TIMESTAMP
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a VARCHAR value containing the Linux system time of query execution in a format that can be used as a Date/Time Expression.
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CURRENT_EPOCH
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an INTEGER value containing the current  epoch number
An epoch represents committed changes to the data stored in a database between two specific points in time. In other words, an epoch contains all COPY, INSERT, UPDATE, and DELETE operations that have been executed and committed since the end of the previous epoch.
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K_SAFETY_LEVEL
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an INTEGER value containing the K-Safety level of the database (see MARK_DESIGN_KSAFE)
K represents the maximum number of nodes in a database that can fail and recover with no loss of data. In Vertica V2.1, the value of K can be zero (0) or one (1). The value of K can be one (1) only when the Physical Schema design meets certain requirements. The designs generated by the Database Designer are K-Safe.
A physical schema consists of a set of projections used to store data on disk. The projections in the physical schema are based on the objects in the Logical Schema.
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CATALOG_REV_NUM
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an INTEGER value containing the catalog version number
In Vertica, the catalog is a set of files that contain information (metadata) about the objects in a database (nodes, tables, constraints, projections, etc.) The catalog is replicated on all nodes in a cluster.
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TUPLE_MOVER_MODE
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a VARCHAR value containing the tuple mover mode (bulk mode or normal)
The tuple mover is the component of Vertica that moves the contents of the Write Optimized Store (WOS) into the Read Optimized Store (ROS). This data movement is known as a moveout. Normally, the tuple mover runs automatically in the background at preset intervals and is referred to as the ATM.
The ROS (Read Optimized Store) is a highly optimized, read-oriented, physical storage structure that is organized by projection and that makes heavy use of compression and indexing. You can use the COPY...DIRECT and INSERT (with direct hint) statements to load data directly into the ROS.
Compression is the process of transforming data into a more compact format. Compressed data cannot be directly processed; it must first be decompressed. Vertica uses integer packing for unencoded integers and LZO for compressible data. Although compression is generally considered to be a form of encoding, the terms have different meanings in Vertica.
LZO is an abbreviation for Lempel-Ziv-Oberhumer. It is a data compression algorithm that is focused on decompression speed. The algorithm is lossless and the reference implementation is thread safe.
The WOS (Write Optimized Store) is a memory-resident data structure into which INSERT, UPDATE, DELETE, and COPY (without DIRECT hint) actions are recorded. Like the ROS, the WOS is arranged by projection but it stores tuples without sorting, compression, or indexing and thus supports very fast load speeds. The WOS organizes data by epoch and holds uncommitted transaction data.
Compression is the process of transforming data into a more compact format. Compressed data cannot be directly processed; it must first be decompressed. Vertica uses integer packing for unencoded integers and LZO for compressible data. Although compression is generally considered to be a form of encoding, the terms have different meanings in Vertica.
LZO is an abbreviation for Lempel-Ziv-Oberhumer. It is a data compression algorithm that is focused on decompression speed. The algorithm is lossless and the reference implementation is thread safe.
The ROS (Read Optimized Store) is a highly optimized, read-oriented, physical storage structure that is organized by projection and that makes heavy use of compression and indexing. You can use the COPY...DIRECT and INSERT (with direct hint) statements to load data directly into the ROS.
Compression is the process of transforming data into a more compact format. Compressed data cannot be directly processed; it must first be decompressed. Vertica uses integer packing for unencoded integers and LZO for compressible data. Although compression is generally considered to be a form of encoding, the terms have different meanings in Vertica.
LZO is an abbreviation for Lempel-Ziv-Oberhumer. It is a data compression algorithm that is focused on decompression speed. The algorithm is lossless and the reference implementation is thread safe.
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