Locking in HDAM, PHDAM, HIDAM, and PHIDAM databases

If you access a HIDAM or PHIDAM root through the index, a lock is obtained on the index, using the RBA of the root segment as the resource name. Consequently, a single lock request locks both the index and the root.

When NOTWIN pointers are specified on a PHIDAM root, a lock on the next higher non-deleted root is required to provide data integrity. IMS obtains the additional lock by reading the index until a non-deleted index entry is found and then locking the RBA of the root segment as the resource name.

When you access an HDAM or a PHDAM database, the anchor of the desired root segment is locked as long as position exists on any root chained from that anchor. Therefore, if an update PCB has position on an HDAM or PHDAM root, no other user can access that anchor. When a segment has been updated and the IRLM is used, no other user can access the anchor until the user that is updating commits. If the PI lock manager is used and an uncommitted unit of work holds the anchor, locks are needed to access all root and dependent segments chained from the anchor until the user that is updating commits.