Database I/O data
This process allows later reporting by transaction, by user (for accounting), and by database, which is always true for the DL/I calls. Each call is counted by type (GU, ISRT, and so on) and per DBD.
These database segments also contain fields for several I/O-related counts. I/O activity is split into categories according to whether the I/O was a read or write, key or non-key access. One additional count, called NO I/O, is unique to BMC AMI Ops Monitor for IMS Offline. This count is a measure of IMS overhead and is the number of requests to the IMS buffer handler that do not result in I/O. These counts can be affected by the Event Collector parameters.
Database reads
Reads are counted as key or nonkey reads.
No database reads are collected if DBIO=NONE (except for DEDBs and MSDBs).
The database read counts are collected at the database level with both DBIO=BFALTERS and DBIO=IOWAITS.
Reads caused by access through a secondary index or logical database are counted with DBIO=BFALTERS and DBIO=IOWAITS, but are shown for the actual target DBD (DBPCB).
For more information about the Event Collector parameters, see .
Database writes
Writes are counted as key and nonkey writes.
No database writes are collected if DBIO=NONE (except for DEDBs).
If DBIO=BFALTERS:
- All writes are collected at the database level.
- Writes to maintain a secondary index or logical database are collected. Counts are maintained at the database level (DBPCB).
If DBIO=I OWAITS:
- Most writes are collected at the transaction level and reported under the database entry ALLDBS , including all writes occurring at sync point (the majority). These counts correspond closely to the DC Monitor IWAITS that are reported under the I/O PCB (Program I/O report).
- Database writes that occur during call processing (such as the deletion of a HISAM root) are accumulated by database.
- Writes to maintain a secondary index or logical database are collected under the DBD that is the actual target (DBPCB).
- VSAM-initiated writes for buffer steal and background write are not measured.
- OSAM buffer steal writes are accumulated in the (otherwise unused) NO I/O counter for the database/transaction whose read request forced the buffer steal.
- Chained VSAM or OSAM writes of multiple buffers count as one write.
NO I/O
NO I/O counts are collected only if DBIO=BFALTERS.
NO I/O measures the number of requests to the IMS buffer handler that do not result in I/O.