Enabling Dynamic Extend for Datacom areas

Products

• Datacom/DB
• Datacom
• Datacom/AD

Issue/Introduction

How can the Dynamic Extend feature be enabled for a Datacom area so that it can be dynamically extended when it becomes full?

Environment

Release: 19.0

Resolution

To turn on and enable dynamic extend for a Datacom area, run DDUPDATE and change the DYNAMIC-EXTEND and DYN-EXT-TRACKS attributes in the area.
The 1000 ALTER and 1500 transactions can be used to change the attributes in the PROD version in datadictionary and directly in the CXX without having to close and catalog the database.
If using Dataquery follow the 1000 ALTER transaction group with a 1000 ENABLE transaction group.
For the purpose of turning on dynamic extend for the area, the ENABLE is not needed but It is good practice to do the ENABLE anyway in case Dataquery is used in the future against the database.

For example, to enable dynamic extend for an area with 100 cylinders code the following:

-USR DATACOM-INSTALL,NEWUSER
-UPD AREA,area-occurrence-name(PROD)
1000 ALTER 
1500 DYNAMIC-EXTEND,C 
1500 DYN-EXT-TRACKS,100
-END 
-UPD AREA,area-occurrence-name(PROD)      
1000 ENABLE                           
-END  

Alternatively if you are updating many areas in the same database you can do one ENABLE for the database after all the AREA ALTERs.

-USR DATACOM-INSTALL,NEWUSER
-UPD DATABASE,database-occurrence-name(PROD)
1000 ENABLE
-END

To enable dynamic extend for the IXX change the DYNAMIC-EXTEND and DYN-EXT-TRACKS attributes in the database entity.

-USR DATACOM-INSTALL,NEWUSER
-UPD DATABASE,database-occurrence-name(PROD)
1000 ALTER 
1500 DYNAMIC-EXTEND,C 
1500 DYN-EXT-TRACKS,100
-END
-UPD DATABASE,database-occurrence-name(PROD)
1000 ENABLE
-END  

To specify tracks instead of cylinders change the DYNAMIC-EXTEND attribute to specify T instead of C: 

1500 DYNAMIC-EXTEND,T 

To turn off dynamic extend, set the DYNAMIC-EXTEND attribute to N.

1500 DYNAMIC-EXTEND,N 

The number of extents is limited by the operating system; there is a limit of 16 extents per volume for non-SMS datasets. SMS allows for more extents. 

The DYNAMIC_EXTEND console command can be used to run an on-demand Dynamic Extend. Please refer to article How to extend a Datacom area while the database is open for more details.

Additional Information

See the Datacom documentation section 1000 ALTER Transaction for more information about the DDUPDATE command to enable Dynamic Extend processing.