Measure Reference Manual

Legacy Style Only Counter Field DDL Definition for DISKFILE Entities
This counter field is used in Legacy Style DDL records only.
OPEN-QLEN-MAX
(Legacy Style only) Maximum number of opens on this file.
Counter type: Max queue.
Usage Notes for All DISKFILE Entities
• Both DISCOPEN and DISKFILE measure physical access to a file. When you decide when to
use DISCOPEN and when to use DISKFILE, consider:
◦ DISCOPEN creates a separate counter record for each file open. Opener processes are
identified individually. If the same process opens a file more than once, multiple DISCOPEN
records are created.
◦ DISKFILE measures disk file access collectively for a file as a whole. DISKFILE creates one
counter record per measured file and does not track individual opener processes.
◦ For indirect opens, such as an open of an alternate-key file, DISCOPEN creates a separate
record. DISKFILE does not create a separate record for indirect opens.
◦ Both DISCOPEN and DISKFILE create a new record if a file closes and reopens during a
measurement.
◦ DISCOPEN provides a detailed view of disk file activity. DISCOPEN counters are especially
useful for detecting potential problems with the structure of key-sequenced database files.
◦ If you do not need a high level of detail, DISKFILE reduces the amount of data you must
analyze while still letting you detect potential problems with file structure and contention.
To measure logical access to a file, use the FILE entity type. For a description, see FILE
(page 227).
• DISCOPEN and DISKFILE entities count requests to the storage driver software. These counts
do not distinguish between requests that are satisfied out of cache (logical request only) and
requests that are satisfied through an I/O transfer (physical I/O).
In writes to mirrored disks, the request counts are incremented once even though two physical
writes occurred.
Usage Notes for G-Series DISKFILE Entities
• The counters SQL-INSERTS, SQL-UPDATES, and SQL-DELETES are available starting with DP2
(T9053G08) and the G06.11 RVU. The counter SQL-ENDING-ROWS is available with DP2
(T9053G09) and the G06.12 RVU.
• The SQL-ENDING ROWS counter is of interest for SQL tables used to represent a queue.
Following the initial open of a file, this value is not displayed and is reported in the external
records as a -1 until the number of rows in the table has been zero at some time. Once the
number of rows is equal to zero (for example, an empty queue), the counter tracks the number
of rows in the file at the end of each interval.
• In Measure G08 and later PVUs, the DISKFILE entity report identifies whether the disk file is
file format 1 or 2. A format 2 file is used when:
◦ The maximum size of an unpartitioned file (or of any partition of a partitioned file) exceeds
2 GB - 1 MB.
◦ A non-key-sequenced partitioned file has a maximum size equal to or greater than 4 GB.
DISKFILE 225