APT Scripts

create_xviews.sql

Some APT scripts are based directly on the X$ tables, rather than the V$ views. This is necessary where the V$ views do not expose the required information, or where it would be inefficient to query them.

Because the X$ tables are only visible to the SYS schema, and because it would be bad practice to do anything as SYS unnecessarily, these scripts require that one create a set of X_$ views that expose the X$ tables to other DBA schemata.

This script creates an X_$ view for every X$ table. It must be run as SYS from SQL*Plus.

View script for: 7.3, 8.0 or 8.1

reset_sqlplus.sql

This script is called by many of the other scripts. It is used to return SQL*Plus to a known condition.

View script for: all releases


hidden_parameters.sql

This script lists all the hidden parameters, together with their descriptions and whether they can be modified. Note that to modify a hidden parameter with the ALTER SESSION or ALTER SYSTEM statements, it is necessary to enclose the parameter name in quotation marks. See the 8.1 version of the APT script tune_spin_count.sql for an example.

View script for: 7.3  8.0 or 8.1

all_parameters.sql

This script reports the values of all parameters including the hidden parameters.

View script for: 7.3  8.0  8.1


resource_waits.sql

Resource waits can often be (nearly) eliminated by database server level tuning. This script shows the major resource types waited for over the life of the instance, in order of severity. It can be used to focus reactive tuning.

The average waiting time shown is the average waiting time for each logical wait. A logical wait may be composed of multiple distinct waits, all but the last of which timed out.

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View script for: 7.3  8.0 or 8.1

routine_waits.sql

The average waiting time for routine waits, such as I/O waits, can also be improved by database server level or operating system level tuning. This script reports the average waiting time for these routine waits.

View script for: 7.3  8.0 or 8.1

system_times.sql

This script reports the total waiting time for both routine and resource waits, together with the CPU time used. The relative contribution of each type of wait to overall response times, and the potential benefit of tuning actions, can be estimated from this information.

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View script for: 7.3, 8.0 or 8.1

session_times.sql

When a user reports an episode of poor performance, this script can be used to determine whether their session has been working (say on an inefficient query) or waiting for resources, and if so, which resources they have been waiting for. Idle waits are not excluded.

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View script for: 7.3, 8.0 or 8.1

resource_waiters.sql

If there has been extensive waiting for a particular type of resource, then this script can be used to determine which extant sessions have contributed to or been affected by the problem.

View script for: 7.3, 8.0 or 8.1

trace_waits.sql

This script is one of our favorites. It finds the top N sessions that have been affected by a particular type of resource wait, and enables event 10046, level 8 in those sessions for the specified period. This event captures every wait event and its wait parameters, and writes the information to the process trace file together with the normal sql_trace output. The wait parameters can then be analyzed to understand exactly what is causing the performance problem.

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View script for: 7.3, 8.0 or 8.1


latch_sleeps.sql

If there are latch free waits, then this script can be used to further diagnose the problem. For each latch type, it reports the estimated impact of sleeps, and the number of sleeps per get. It also reports the number of other waits while holding each latch type, together with the latch level.

To reduce latch free waits, one should concentrate on the latches with the greatest impact. However, if there are a significant number of other waits while holding those latches, then one should regard those sleeps as a secondary symptom of another problem, such as contention for a higher level latch.

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View script for: 7.3, 8.0 or 8.1

latch_gets.sql

This script reports the breakdown of willing-to-wait gets for each latch type, into simple gets, spin gets and sleep gets. Spin gets and sleep gets are latch gets that require spinning or sleeping respectively. Simple gets require neither.

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View script for: 7.3, 8.0 or 8.1

latch_spins.sql

This script compares spin gets to sleep gets as an indicator of the effectiveness of spinning, for each latch type.

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View script for: 7.3, 8.0 or 8.1

tune_spin_count.sql

This script can be used to dynamically tune the _spin_count parameter of an active instance. It first reports the spin hit rate and average cost of spinning over the life of the instance so far. It then prompts the user to dynamically modify the spin count and wait for a while to measure the effectiveness of the change. After waiting, the spin hit rate and average cost of spinning over the interval are reported. Under uniform load, this script can be run several times to find the optimum spin count range.

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View script for: 7.3 or 8.0  8.1

latch_types.sql

This scripts prints a list of the latch types, and reports the number of child latches for each type. If a latch type has multiple child latches, V$LATCH_CHILDREN can be used to determine whether activity against the child latches is evenly distributed. V$LATCH_PARENT should also be checked to see whether there has been any activity against the parent latch.

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View script for: 7.3  8.0 or 8.1

latch_where.sql

For those who are very familiar with the layers of the Oracle architecture and their functionality, this script may help them to know where in the code latch requests are failing.

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View script for: 7.3  8.0 or 8.1


fixed_table_hwms.sql

This script is for release 7.3 only. It reports the high water mark usage of the fixed tables that are sized by an init.ora parameter. This is useful to avoid the two extremes of either running out of slots in these tables, or making them so large as to be wasteful. From release 8.0, this script is redundant, because V$RESOURCE_LIMIT provides the same information.

View script for: 7.3

enqueue_stats.sql

This script looks at X$KSQST, which contains a breakdown of enqueue gets and enqueue waits by lock type. Unfortunately, there is no indication of the relative duration of these waits, so care must be taken when interpreting the output.

View script for: 7.3  8.0 or 8.1

enqueue_locks.sql

Most blocking lock detection scripts fail to consider that processes waiting for, but not yet holding, a lock can block other processes that need a conflicting lock on the same resource. To resolve such problems, it is essential to consider the order of waiters.

This script shows all the locks that are held or wanted for each resource, together with the number of seconds since the lock was granted or requested respectively, in order. This script is intended to supplement other blocking lock detection scripts such as Oracle's utllockt.sql.

View script for: 7.3, 8.0 or 8.1


lock_element_lwm.sql

In Oracle parallel server, if fine-grained locking is being used, it is normally desirable to have free lock elements at all times (except in VLM environments). This script shows the low water mark of the lock element free list in release 8.0 and beyond.

View script for: 8.0 or 8.1


fixed_table_columns.sql

This script generates a description of all the X$ tables, listing all their columns and their datatypes. We use this whenever we are exposed to a new version of Oracle to see what has changed at the level of the X$ tables.

View script for: 7.3, 8.0 or 8.1

fixed_view_text.sql

This script extracts the SQL statement text for all the V$ views. The V$ views are based on the X$ tables, and reading the SQL statements for these views is the best way to develop an initial understanding of the X$ tables.

View script for: 7.3, 8.0 or 8.1

keep_sys_packages.sql

Marking objects for keeping in the library cache is vital to shared pool performance. This script does the bare minimum of keeping four of the key SYS packages.

View script for: 7.3, 8.0 or 8.1

keep_sequences.sql

From Oracle 7.3, the sequence cache has been part of the library cache, and thus part of the shared pool. A side-effect has been that cached sequence numbers can be aged out of the shared pool and thus lost.

This script marks all cached sequences in the database for keeping, so that sequence numbers will never be lost due to aging out of the shared pool.

View script for: 7.3, 8.0 or 8.1

keep_schema.sql

This script is intended to be used at instance startup to keep all the stored objects in the key application schemata.

View script for: 7.3 or 8.0  8.1

keep_cursors.sql

Cursors that are executed repeatedly should also be kept. That is what this script does.

View script for: 7.3  8.0 or 8.1

nice_shared_pool_flush.sql

Flushing the shared pool is the only way of coalescing free space in the shared pool, and has little performance impact if everything is kept that should be, particularly if done out of peak hours. In 7x24 environments, we favor flushing the shared pool daily to reduce risk of shared pool problems.

This script first calls keep_cursors.sql and keep_sequences.sql prior to flushing, to minimize the unwanted side-effects of flushing the shared pool.

View script for: 7.3, 8.0 or 8.1

shared_pool_lru_stats.sql

The shared pool has two LRU lists for unpinned recreatable chunks - one for transient objects, and one for recurrent use objects. This script shows the current length of the transient and recurrent LRU lists, together with the number of chunks that have been flushed (aged out) and the number of other LRU list operations (adds and removes). These statistics provide feedback on the size of the shared pool.

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View script for: 7.3  8.0 or 8.1

shared_pool_free_lists.sql

Free chunks in the shared pool are maintained on a number of free lists, according to the chunk size. This scripts reports the length and total available free memory on each free list. Long free lists are a major cause of shared pool latch contention.

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View script for: 7.3  8.0 or 8.1

shared_pool_spare_free.sql

If the shared pool is oversized, some spare free memory will be reserved for some time in the main permanent memory chunk within the shared pool. This script shows how much such memory remains (if any).

View script for: 7.3  8.0 or 8.1

shared_pool_summary.sql

This script gives an indication of the balance between free, recreatable, freeable and permanent memory in the shared pool, as well as a breakdown of the chunks and their usage.

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View script for: 7.3  8.0 or 8.1

reserved_pool_hwm.sql

From Oracle 8.0, the reserved part of the shared pool defaults to 5% of the size of the pool. In many cases, this is wasteful. One can use this script to see how much of the reserved pool is actually being used.

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View script for: 7.3  8.0  8.1


Copyright 1999 Ixora Pty Ltd