[TRAFODION-2508] Document CQD for sort scratch disk selection

• Type: Documentation
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.1-incubating
• Component/s: documentation
• Assignee: Liu Yu
• Reporter: Sandhya Sundaresan
• Created: 25/Feb/17 05:42
• Updated: 19/May/17 00:45
• Resolved: 19/May/17 00:45

Description

https://issues.apache.org/jira/browse/TRAFODION-2146

STFS_HDD_LOCATION is set in ms.env as part of install. This is by default the location of overflow disks. To make a change to this setting requires trafodion to be bounced.

The cqd option has been added. This option allows setting the overflow disks in the form of CQD in the defaults table. This does not require trafodion to be restarted to make the overflow disk settings effective.
The format for specifying the scratch disks is as follows :
control query default SCRATCH_DIRS ‘/tmp2:/tmp3:/tmp4/scratch’
Currently STFS_HDD_LOCATION is used by default. CQD option is available if STFS_HDD_LOCATION needs to be overridden in the field if customer configured disk changes.
It’s basically a “:” separated list of directories. Ensure all these disks on every node exist and that each of these directories has Trafodion access.
Scratch files of format SCR<*****> are created in the newly specified directories when queries that need to overflow like sort and hash join queries are run.
Possible errors :
If the format of the directories is incorrect or they don’t exist on the system, an error will be returned when the query is prepared – compile time.
If the user does not have Trafodion access the query may fail at runtime.

Issue Links

• is a clone of: TRAFODION-2521 Add SCRATCH_DISKS CQD