Specifies the amount (in bytes) of the total memory used for query execution.

Notes:

For more information, see Memory Settings.

Limits: 32 MB to 256 TB

Default: 0 (use 50% of the physical system memory)

Specifies the maximum amount of memory that will be overallocated (reserved as virtual memory) for zero-cost growing of certain memory areas. The setting needs to be changed only in rare cases.

A value of 0 means no overallocation. A value of ‑1 means overallocate with the amount of total system memory ("unlimited").

Default: 2G or set to 0 upon installation if the system does not allow overallocation.

Enables the huge pages feature of the CPU only for queries using the number of cores less than or equal to the specified value. Set this option to 1 if parallel queries do not benefit from the huge pages feature. This may be experienced on some operating systems, such as Red Hat Enterprise Linux 6, which has an automatic anonymous TLB feature.

Special value 0 means there is no limit.

Default: 0 (no limit)

Specifies whether to use the huge pages feature (see Using Large Pages) of the CPU. Valid values are true and false.

Default: false

Specifies whether to use NUMA optimization (see Using NUMA Optimization). Valid values are true and false.

Default: true

Specifies whether all blocks are to be rewritten by the COMBINE command. Setting this option to true can be used to avoid or undo block fragmentation introduced by partial update propagation.

Default: false

Specifies whether all blocks are to be rewritten by the system-triggered propagation process. Setting this option to true can be used to avoid block fragmentation introduced by partial update propagation.

Default: false

Specifies the maximum size for the main_wal_backups directory, which holds old main.wal files.

Default: 2 GB

Specifies the number of processing units in the system. This value is used to calculate the amount of memory available for each transaction.

Num_cores is used to calculate the maximum parallelism level for a newly issued query if there are many queries already being executed. The goal is not to deteriorate the total throughput of the system. Generally, the higher the num_cores value, the higher parallelism levels are granted for queries running concurrently (where each parallelism level is not higher than max_parallelism_level).

Num_cores is used to derive a database-wide target on the number of concurrent threads used for parallel execution. Queries will run at a lower degree of parallelism if the default or requested degree would lead to an uneven allocation of resources to the new query based on the number of concurrently executing queries. On a system running many concurrent queries, new queries may get only one core and will more likely run out of memory since the num_cores value is used to reserve memory for possible other threads.

Default: Number of processors visible to the operating system.

Tells X100 whether to attempt to merge concurrent updates on the same table. If set to false, the transaction that tries to commit last will fail and will have to abort. Disabling merging of concurrent updates can reduce memory consumption, especially if there are any long-running transactions in the system.

Default: true

Uses SSE4.2 for accelerated string processing on CPU architectures that support it.

Default: YES

The Positional Delta Tree (PDT) is a data structure used for batch updates residing in memory.

Specifies the number of profiles to keep in memory for a database. If exceeded, oldest profiles are dropped.

Default: 1

Specifies the number of profiles to keep in memory for a session.

Default: 1

Specifies the TCP/IP port on which the X100 server will listen for connections.

If zero or omitted, the server will dynamically assign a port when it first starts up. A nonzero value should only be defined in a database specific vectorwise.dbname.conf; it must not be defined in the installation-wide vectorwise.conf.

A fixed nonzero port number can be useful in situations where remote direct connections are needed, such as from the vwload utility, and there is a firewall between the client and server. In such cases, the fixed port can be made known to the firewall to allow vwload to connect to the X100 server. The system administrator should choose a port that does not conflict with other listen ports on the network.

Default: 0

Generates a profile file for each query. The profiles will be saved in the directory dbname/CBM/profiles in timestamp-named files. Valid values: true and false.

Default: false

Specifies the directory to which profile files are written when using profile_per_query = true.

The installation owner must have write permission to the directory.

Default: empty

Specifies the maximum number of profile files retained when using profile_per_query = true. When this threshold is exceeded, the profile files are deleted (starting from the oldest ones) until the limit is met.

Default: 1000

Specifies the maximum total size (in bytes) of profile files retained when using profile_per_query = true. When this threshold is exceeded, the profile files are deleted (starting from the oldest ones) until the limit is met.

Default: 100M

Collects and prints profiling information. Setting this parameter to false may give the highest performance on short-running queries.

Default: true

Specifies the minimum I/O granularity.

This option is the most important for I/O performance.

Default: 512K

Specifies the buffer pool size in bytes (that is, disk cache). The setting can be changed without reloading data.

For more information, see Memory Settings.

Default: 0 (use 25% of the physical system memory)

Enables or disables compression of string data using the LZ4 method. Valid values are true and false.

Setting this parameter to true may give better performance on IO-constrained systems.

Default: false

Tells the X100 server whether to check if the operating system supports gather I/O and to use asynchronous gather I/O if it does. Valid values are true and false.

Default: true

Specifies the number of blocks that are grouped together on disk to improve data locality for sequential scans.

Default: 8

Specifies the granularity of the (automatically created) min-max indexes on all columns. Min-max indexes are used automatically to derive scan ranges based on selection predicates on columns that correlate to tuple order.

The value of this parameter influences the precision of the range restrictions applied when performing a table scan. With a default setting (1024), up to ~0.1% of a table might be scanned extra for each found scan range. Increasing this value can improve precision, but may slightly decrease the update performance and increase the memory usage. We recommend increasing this parameter only if you issue queries that scan small fractions of a table.

This parameter should be set before database creation.

Default: 1024

Enables or disables the Predictive Buffer Manager, which improves performance in workloads that are I/O bound. Valid values are true and false. Setting the parameter to false switches X100 back to using the Least Recently Used (LRU) algorithm.

PBM improves performance in most cases. On rare occasions, however, the LRU algorithm can be faster because it is simpler and incurs less overhead, especially in scenarios where data is fully memory-resident (no blocks are loaded or swapped out during query execution).

Default: true

Enables or disables spilling to disk for hash aggregations. Enabling this option prevents out-of-memory conditions from occurring when aggregate results are too large to fit into memory. Valid values are true and false.

Default: false

Enables or disables spilling to disk for hash joins. Enabling this option prevents out-of-memory conditions from occurring when the hash table built from one of the join inputs is too large to fit into memory. Valid values are true and false.

Default: false

Enables or disables spilling to disk for reused repeating query plan parts. Enabling this option prevents out-of-memory conditions from occurring when the buffered output of a reused query part is too large to fit into memory. Valid values are true and false.

Default: false

Specifies the maximum result length of the LISTAGG() aggregate function in ASCII bytes.

Limits: 1 to 32000

Default: 4000

Defines the maximum number of threads used by a single query. This is a hard limit.

A value of 1 disables parallel query execution. A value larger than 1 enables parallel query execution.

Max_parallelism_level is related to the num_cores parameter (see num_cores). The execution engine tries not to use more than the max_parallelism_level number of cores at a time for any query.

Limits: 0 to 256

Default: Number of processors on the machine or 8 if the machine has more than 8 processors.

Defines the maximum number of threads used by update (DML) queries. This setting can be used to improve performance of update queries that can benefit from parallelization. Special values:

Defines the forced level of parallelism used by update (DML) queries. This setting can be used to improve performance of update queries that can benefit from parallelization. Values: