Terms Used in This Guide
You should be familiar with the following terms and definitions. Some of these terms will assist you in interpreting the monitoring data displayed by IPM.
A blocking lock is a lock granted on a resource in such a way as to prevent another lock from being granted on that same resource. For example, an exclusive lock on a table prevents another shared or exclusive lock from being granted on that table. A blocking lock serializes access to a resource, table, page, or database. For example, an exclusive lock on a table blocks all other access to that table. Until the transaction holding the lock completes (commits or rolls back), all other transactions must wait.
Note: A blocking lock is not a deadlock.
A deadlock is a condition that occurs when one transaction is waiting for a lock held by another transaction at the same time that the other transaction is waiting for a lock held by the first. Both transactions block each other from completing.
A lock list is a list of one or more locks on resources in a given database or servers. Each session has at least one lock list. When a session is in a transaction, that session has an additional lock list containing all the locks acquired during the transaction.
A logical lock is a lock that is usually acquired during a transaction and released during a transaction or at commit time. A page lock is a logical lock.
A physical lock is a lock that can span multiple transactions in any given session. In most cases, table and database locks are held from the point that they are acquired until the end of the session.
A resource is any object in a database on which a lock can be held. A table, a page in a table, or even a database is a resource.
A command is an operation that you execute at the operating system level. An extended operation invoked by a command is often referred to as a utility.
A statement is an operation that you embed within a program or execute interactively from a terminal monitor. A statement can be written in Ingres 4GL, a host programming language (such as C), or a database query language (SQL or QUEL).