For more information on these ratios, see the Oracle7 Tuning Guide. For information on the MIB variables that are used to calculate these ratios, see Appendix A, "Oracle Database MIB Reference."
| Block Changes Per Transaction | This ratio measures the amount of DML work that each transaction performs. Creating or dropping indexes impacts this value, because changes to index blocks increment it. |
| oraDbSysDbBlockChanges / oraDbSysUserCalls | |
| Block Get Rate | This ratio determines the block get rate. The block get rate is a basic measure of the rate at which the application system references the database. The time unit typically used in this ratio is one second. |
| (oraDbSysConsistentGets + oraDbSysDbBlockGets) / time unit | |
| Block Visits Per Transaction | This ratio measures the work database load imposed per transaction; if it is moving independently, then this strongly indicates that there has been a change in the application workload. |
| (oraDbBlockGets + oraDbSysConsistentGets) / oraDbSysUserCommits | |
| Cache Hit Ratio | This ratio measures the effectiveness of the buffer cache. The normally acceptable range is 70 - 85%. |
| (oraDbSysConsistentGets + oraDbSysBlockGets - oraDbSysPhysReads) / (oraDbSysConsistentGets + oraDbSysBlockGets) | |
| Call Rate | This ratio measures the work demand rate being placed on the instance from all work sources. It should be noted, however, that this rate may not be directly comparable across application system version changes where row at a time loop constructs have been recoded as set operations or vice versa. Use of the array interface will also affect this ratio. |
| (oraDbSysRecursiveCalls + oraDbSysUserCalls) / time unit | |
| Calls Per Transaction | This ratio measures the number of client requests made per transaction. Calls per transaction can be used to detect changes in the application, or in the ways in which it is being used. This value may rise sharply as ad hoc queries increase. |
| oraDbSysUserCalls / oraDbSysUserCommits | |
| Changed Block Ratio | This ratio measures the balance between queries and DML within this database application. Changes in this ratio indicate and/or quantify changes in indexation or application usage. |
| oraDbSysDbBlockChanges / (oraDbSysBlockGets + oraDbSysConsistentGets) | |
| Consistent Change Ratio | This ratio measures the extent to which applications are having to exercise the read consistency mechanism. In this connection, it is important to realize that the query processing parts of UPDATE and/or DELETE operations are subject to read consistency. |
| oraDbSysConsistentChanges / oraDbSysConsistentGets | |
| Continued Row Ratio | This ratio should be very close to zero, except in applications handling long LONG columns. If this ratio increases over time, usually PCTFREE has been set too low on one or more tables. |
| oraDbSysTableFetchContinuedRow / (oraDbSysTable FetchRowid + oraDbSysTableScanRows) | |
| Library Cache Miss Ratio | If this ratio begins to rise, then resource usage can be expected to increase. A rising library cache miss ratio may be due to wider use of application functionality causing more SQL statements and stored procedures to be active than had previously been the case. |
| (oraDbLibraryCachePins - oraDbLibraryCacheReloads) / oraDbLibraryCachePins | |
| Recursive to User Call Ratio | Under Oracle7, a change in this ratio can reflect an application change, or indicate a need to adjust the size of the shared pool. Any marked change in the DDL load also affects this ratio. |
| oraDbSysRecursiveCalls / oraDbSysUserCalls | |
| Redo Log Space Wait Ratio | This ratio measures memory allocation. If it is greater than 1 / 5,000, then the redo log buffer should be increased until the redo log space wait ratio stops failing. |
| oraDbSysRedoLogSpaceRequests / oraDbSysRedoEntries | |
| Row Source Ratio | This ratio measures the percentage of the total rows retrieved which came from full table scans. As soon as this percentage starts to rise much above 0, the interpretation of other statistics may need to be reviewed. |
| oraDbSysTableScanRows / (oraDbSysTableFetchRowid + oraDbSysTableScanRows) | |
| Sort Overflow Ratio | oraDbSysSortsDisks / (oraDbSysSortsMemory + oraDbSysSortsDisks) is the sort overflow ratio. This ratio yields the ratio of the number of sorts which are using temporary segments. Under restricted circumstances when there is a predominance of medium size sorts, increasing the sort area size may be effective. |
| oraDbSysSortsDisks / (oraDbSysSortsMemory + oraDbSysSortsDisks) | |
| Transaction Rate | The transaction rate is a basic measure of application work, and would be calibrated in transactions per second (tps) for a typical OLTP benchmark. Administrators should be particularly concerned if a fall in this value is associated with a rise in the number of connected users or vice versa. Changes in application structure or work patterns can also distort this figure. |
| oraDbSysUserCommits | |
| User Call Rate | This rate measures the work demand rate being posed by client side applications running under the instance. It should be noted, however, that this may not be directly comparable across application system version changes where code has been moved from client to server side or vice versa. |
| oraDbSysUserCalls | |
| User Calls Per Parse | This ratio indicates how well the application is managing its context areas. If it changes, then application change is the most likely explanation, but it may also indicate that usage patterns are changing and users are moving from one module to another either more frequently or less frequently. |
| Although the shared SQL area makes the maximizing of this ratio less important than with earlier versions of Oracle, it is still possible to reduce resource usage by raising this ratio. | |
| oraDbSysUserCalls / oraDbSysParseCount | |
| User Rollback Ratio | oraDbSysUserRollbacks / (oraDbSysUserCommits + oraDbSysUserRollbacks) is the user rollback ratio. The user rollback ratio indicates the rate at which application transactions are failing. Rolling back a transaction uses significant resources, and would seem to indicate that all of the resources expended in executing the transaction have been wasted. |
| oraDbSysUserRollbacks / (oraDbSysUserCommits + oraDbSysUserRollbacks) | |