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SQL/MX Glossary

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Glossary
HP NonStop SQL/MX Glossary—523732-002
Glossary-19
lock escalation
lock escalation. The replacement of all the row locks on a partition or table by a single
partition lock or table lock when the number of row locks approaches a limit. See also
lock granularity.
lock exclusion mode. A lock attribute that determines whether any process except the lock
holder can access the locked data. See also exclusive lock and shared lock.
lock granularity. The size of a lockable unit. A lockable unit can be a single row (row lock),
a subset of the rows in a table, a partition of a table or a nonpartitioned table (partition
lock), or an entire partitioned table (table lock).
lock holder. The process that acquires an exclusive or shared lock on data, sometimes
called lock owner.
lockable unit. The amount of data that can be protected by a single lock. Tables, partitions
of tables, subsets of rows in a table, and single rows are lockable units. See also lock
granularity.
M
MACL. SQL/MX administrative command library. A library of administrative commands,
linked into MXCI, that supports manipulation of logical objects defining the user-visible
attributes of the SQL/MX connectivity services (MXCS). See MXCS.
MDAM. MultiDimensional Access Method. An optimized scan method that provides
improved performance for queries that contain range or missing predicates on key
columns.
MDF. See module definition file (MDF).
merge join. See sort merge join.
metadata tables. Tables that store information about all SQL objects within a database.
The system metadata is created and maintained by the system as users create, alter,
or drop objects. Contrast with user metadata tables.
method. See Java method.
MGSS. See Module Group Specification String (MGSS).
Microsoft ODBC. Open Database Connectivity. A specification for an application
programming interface (API) that defines a standard set of routines that an application
can use to access a database. ODBC is based on the call level interface (CLI)
specifications from X/Open and ISO/IEC for database APIs and uses structured query
language (SQL) as its database access language. By calling ODBC functions through
database-specific drivers, which are loaded at run time, an application can access
different databases by using the same source code. See also NonStop ODBC/MX
association server.