MARK_DESIGN_KSAFE

Enables or disables high availability in your environment, in case of a failure.

Enables or disables high availability in your environment, in case of a failure. Before enabling recovery, MARK_DESIGN_KSAFE queries the catalog to determine whether a cluster's physical schema design meets the following requirements:

  • Small, unsegmented tables are replicated on all nodes.

  • Large table superprojections are segmented with each segment on a different node.

  • Each large table projection has at least one buddy projection for K-safety=1 (or two buddy projections for K-safety=2).

    Buddy projections are also segmented across database nodes, but the distribution is modified so segments that contain the same data are distributed to different nodes. See High availability with projections.

MARK_DESIGN_KSAFE does not change the physical schema.

This is a meta-function. You must call meta-functions in a top-level SELECT statement.

Behavior type

Volatile

Syntax

MARK_DESIGN_KSAFE ( k )

Parameters

k
Specifies the level of K-safety, one of the following:

  • 2: Enables high availability if the schema design meets requirements for K-safety=2

  • 1: Enables high availability if the schema design meets requirements for K-safety=1

  • 0: Disables high availability

Privileges

Superuser

Return messages

If you specify a k value of 1 or 2, Vertica returns one of the following messages.

Success:

 Marked design n-safe

Failure:

 The schema does not meet requirements for K=n.
 Fact table projection projection-name
 has insufficient "buddy" projections.

where n is a K-safety setting.

Notes

  • The database's internal recovery state persists across database restarts but it is not checked at startup time.

  • When one node fails on a system marked K-safe=1, the remaining nodes are available for DML operations.

Examples

=> SELECT MARK_DESIGN_KSAFE(1);
  mark_design_ksafe
----------------------
 Marked design 1-safe
(1 row)

If the physical schema design is not K-safe, messages indicate which projections do not have a buddy:

=> SELECT MARK_DESIGN_KSAFE(1);
The given K value is not correct;
the schema is 0-safe
Projection pp1 has 0 buddies,
which is smaller that the given K of 1
Projection pp2 has 0 buddies,
which is smaller that the given K of 1
.
.
.
(1 row)

See also