DEDBs and data sharing

You can specify different levels of data sharing for DEDBs. The specifications you make for a DEDB apply to all the areas in the DEDB.

If you specify that a DEDB does not allow data sharing, only one IMS system can access a DEDB area at a time; however, other IMS systems can still access the other areas in the DEDB.

If you specify that a DEDB allows data sharing, multiple IMS systems can access the same DEDB area at the same time. Sharing a single DEDB area is equivalent to block-level sharing of full-function databases.

You can specify the level of data sharing that a DEDB allows by using the SHARELVL parameter in the DBRC commands INIT.DB and CHANGE.DB. If any IMS has already authorized the database, changing the SHARELVL does not modify the database record. The SHARELVL parameter applies to all areas in a DEDB.

You can share DEDB areas directly from DASD or from a coupling facility structure using the Virtual Storage Option (VSO).