Locks and Concurrency
When you do not specify the SPOOL, TEMP, or PERM options, MODIFY USER places an ACCESS lock on the database being altered and thus runs concurrently with all DML requests.
This is not true when you specify the SPOOL, TEMP, and PERM options because they all require an EXCLUSIVE lock.
This statement also places a rowhash‑level WRITE lock on the database for DBC.DBase. The SPOOL, TEMP, and PERM options then place a second lock on the immediate parent for DBC.DBase. For PERM, the second lock is a rowhash‑level WRITE lock. For SPOOL or TEMP, the second lock is a rowhash‑level READ lock.
The SPOOL, TEMP, and PERM options also place a rowhash‑level WRITE lock on DBC.DataBaseSpace. The PERM option then places a second rowhash‑level WRITE lock on the immediate parent for DBC.DataBaseSpace.
See “Activating Permanent Journaling” on page 43 for information about activating permanent journaling for existing tables.
Also see the following topics in this book.