145 DBMS_WORKLOAD_REPLAY

The DBMS_WORKLOAD_REPLAY package provides an interface to replay a workload capture that was originally created by way of the DBMS_WORKLOAD_CAPTURE package. Typically, the DBMS_WORKLOAD_CAPTURE package will be used in the production system to capture a production workload, and the DBMS_WORKLOAD_REPLAY package will be subsequently used in a test system to replay the captured production workload for testing purposes.

Using DBMS_WORKLOAD_REPLAY

Security Model

Security Model

Use of the package is restricted to users with DBA role or EXECUTE_CATALOG_ROLE.

Additionally, the user of the package must have access to the host directory that contains the workload capture files, and one or more hosts that has the Workload Replay Client installed and can be used to drive the captured workload during a database replay.

Summary of DBMS_WORKLOAD_REPLAY Subprograms

This table list the package subprograms in alphabetical order.

Table 145-1 DBMS_WORKLOAD_REPLAY Package Subprograms

Subprogram	Description
CALIBRATE Function	Operates on a processed workload capture directory to estimate the number of hosts and workload replay clients needed to faithfully replay the given workload
CALIBRATE Function	Cancels the workload replay in progress
DELETE_REPLAY_INFO Procedure	Deletes the rows in `DBA_WORKLOAD_REPLAYS` that corresponds to the given workload replay ID
EXPORT_AWR Procedure	Exports the AWR snapshots associated with a given replay ID
GET_REPLAY_INFO Function	Retrieves information about the workload capture and the history of all the workload replay attempts from the related directory
IMPORT_AWR Function	Imports the AWR snapshots associated with a given replay ID
INITIALIZE_REPLAY Procedure	Initializes replay, and loads specific data produced during processing into the database
PREPARE_REPLAY Procedure	Puts the RDBMS in a special "Prepare" mode
PROCESS_CAPTURE Procedure	Processes the workload capture found in `capture_dir` in place
REMAP_CONNECTION Procedure	Remaps the captured connection to a new one so that the user sessions can connect to the database in a desired way during workload replay.
REPORT Function	Generates a report on the given workload replay
START_REPLAY Procedure	Starts the workload replay

CALIBRATE Function

This function operates on a processed workload capture directory to estimate the number of hosts and workload replay clients needed to faithfully replay the given workload. This function returns the results as an XML CLOB.

Syntax

DBMS_WORKLOAD_REPLAY.CALIBRATE (
   capture_dir          IN VARCHAR2,
   process_per_cpu      IN BINARY_INTEGER DEFAULT 4,
   threads_per_process  IN BINARY_INTEGER DEFAULT 50)
  RETURN CLOB;

Parameters

Table 145-2 CALIBRATE Function Parameters

Parameter	Description
`capture_dir`	Name of the directory object that points to the (case sensitive) OS directory that contains processed capture data
`process_per_cpu`	Maximum number of process allowed per CPU (default is 4)
`threads_per_process`	Maximum number of threads allowed per process (default is 50)

Return Values

Returns a CLOB formatted as XML, that contains:

Information about the capture
Current database version
Input parameters to this function
Number of CPUs and replay clients needed to replay the given workload
Information about the sessions captured (total number and maximum concurrency)

Usage Notes

Prerequisite: The input workload capture was already processed using the PROCESS_CAPTURE Procedure in the same database version.
This procedure will return the same results as the workload replay client in calibrate mode, which can be run as follows.
```
$ wrc mode=calibrate replaydir=
```

CANCEL_REPLAY Procedure

This procedure cancels workload replay in progress. All the external replay clients (WRC) will automatically be notified to stop issuing the captured workload and exit.

Syntax

DBMS_WORKLOAD_REPLAY.CANCEL_REPLAY (
   error_msg    IN VARCHAR2 DEFAULT NULL);

Parameters

Table 145-3 CANCEL_REPLAY Procedure Parameters

Parameter	Description
`error_msg`	An optional reason for cancelling the replay can be passed which will be recorded into `DBA_WORKLOAD_REPLAYS`.`ERROR_MESSAGE`. `DEFAULT` is `NULL`

Usage Notes

Prerequisite: A call to the INITIALIZE_REPLAY Procedure, or PREPARE_REPLAY Procedure, or START_REPLAY Procedure was already issued.

DELETE_REPLAY_INFO Procedure

This procedure deletes the rows in DBA_WORKLOAD_REPLAYS that corresponds to the given workload replay ID.

Syntax

DBMS_WORKLOAD_REPLAY.DELETE_REPLAY_INFO (
   replay_id    IN  NUMBER);

Parameters

Table 145-4 DELETE_REPLAY_INFO Procedure Parameters

Parameter	Description
`replay_id`	ID of the workload replay that needs to be deleted. Corresponds To `DBA_WORKLOAD_REPLAYS`.`ID` (Mandatory)

EXPORT_AWR Procedure

This procedure exports the AWR snapshots associated with a stipulated replay ID.

Syntax

DBMS_WORKLOAD_REPLAY.EXPORT_AWR (
   replay_id    IN  NUMBER);

Parameters

Table 145-5 EXPORT_AWR Function Parameters

Parameter	Description
`replay_id`	ID of the replay whose AWR snapshots should be exported. (Mandatory)

Usage Notes

At the end of each replay, the corresponding AWR snapshots are automatically exported. Consequently, there is no need to do this manually after a workload replay is complete, unless the automatic EXPORT_AWR invocation failed.
This procedure will work only if the corresponding workload replay was performed in the current database (meaning that the corresponding row in DBA_WORKLOAD_REPLAYS was not created by calling the GET_REPLAY_INFO Function) and the AWR snapshots that correspond to that replay time period are still available.

GET_REPLAY_INFO Function

This function retrieves information about the workload capture and the history of all the workload replay attempts from the stipulated directory.

Syntax

DBMS_WORKLOAD_REPLAY.GET_REPLAY_INFO (
   dir    IN VARCHAR2)
 RETURN NUMBER;

Parameters

Table 145-6 GET_REPLAY_INFO Function Parameters

Parameter	Description
`dir`	Name of the workload replay directory object (case sensitive). (Mandatory)

Return Values

The procedure returns the CAPTURE_ID which can be associated with both DBA_WORKLOAD_CAPTURE_ID and DBA_WORKLOAD_REPLAYS.CAPTURE.ID to access the imported information.

Usage Notes

The procedure first imports a row into DBA_WORKLOAD_CAPTURES which will contain information about the capture. It then, imports a row for every replay attempt retrieved from the given replay directory into DBA_WORKLOAD_REPLAYS.
The procedure will not insert new rows to DBA_WORKLOAD_CAPTURES and DBA_WORKLOAD_REPLAYS if these views already contain rows describing the capture and replay history present in the given directory.

IMPORT_AWR Function

This procedure imports the AWR snapshots from a given replay.

Syntax

DBMS_WORKLOAD_REPLAY.IMPORT_AWR (
   replay_id       IN   NUMBER,
   staging_schema  IN   VARCHAR2)
  RETURN NUMBER;

Parameters

Table 145-7 IMPORT_AWR Function Parameters

Parameter	Description
`replay_id`	ID of the replay whose AWR snapshots should be exported. (Mandatory)
`staging_schema`	Name of a valid schema in the current database which can be used as a staging area while importing the AWR snapshots from the replay directory to the `SYS` `AWR` schema. The `SYS` schema is not a valid input. (Mandatory)

Return Values

Returns the new randomly generated database ID that was used to import the AWR snapshots. The same value can be found in the AWR_DBID column in the DBA_WORKLOAD_REPLAYS view.

Usage Notes

This procedure will work provided those AWR snapshots were exported earlier from the original replay system using the EXPORT_AWR Procedure.
IMPORT_AWR will fail if the staging_schema provided as input contains any tables with the same name as any of the AWR tables, such as WRM$_SNAPSHOT or WRH$_PARAMETER. Please drop any such tables in the staging_schema before invoking IMPORT_AWR.

INITIALIZE_REPLAY Procedure

This procedure puts the database state in INIT for REPLAY mode, and loads data into the replay system that is required before preparing for the replay (by executing the PREPARE_REPLAY Procedure).

Syntax

DBMS_WORKLOAD_REPLAY.INITIALIZE_REPLAY (
   replay_name     IN  VARCHAR2,
   replay_dir      IN  VARCHAR2);

Parameters

Table 145-8 INITIALIZE_REPLAY Procedure Parameters

Parameter	Description
`replay_name`	Name of the workload replay. Every replay of a processed workload capture can be given a name. (Mandatory)
`replay_dir`	Name of the directory object that points to the OS directory (case sensitive) that contains processed capture data

Usage Notes

Prerequisites:
- Workload capture was already processed using the PROCESS_CAPTURE Procedure in the same database version.
- Database state has been logically restored to what it was at the beginning of the original workload capture.
The subprogram loads data into the replay system that is required before preparing for the replay by calling the PREPARE_REPLAY Procedure.

For instance, during capture we may record the connection string each session used to connect to the server. The INITIALIZE_REPLAY Procedure loads this data and allows the user to re-map the recorded connection string to new connection strings or service points.

Elaborating on the example described in the PROCESS_CAPTURE Procedure, one could invoke the following:
```
DBMS_WORKLOAD_REPLAY.INITIALIZE_REPLAY('replay foo #1', 'rec_dir');
```
This command will load up the connection map and by default will set all replay time connection strings to be equal to NULL. A NULL replay time connection string means that the workload replay clients (WRCs) will connect to the default host as determined by the replay client's runtime environment settings. The user can change a particular connection string to a new one (or a new service point) for replay by using the REMAP_CONNECTION Procedure.

PREPARE_REPLAY Procedure

This procedure puts the database state in PREPARE FOR REPLAY mode.

Syntax

DBMS_WORKLOAD_REPLAY.PREPARE_REPLAY (
   synchronization           IN BOOLEAN  DEFAULT TRUE,
   connect_time_scale        IN NUMBER   DEFAULT 100,
   think_time_scale          IN NUMBER   DEFAULT 100,
   think_time_auto_correct   IN BOOLEAN  DEFAULT TRUE);

Parameters

Table 145-9 PREPARE_REPLAY Procedure Parameters

Parameter	Description
`synchronization`	Turns synchronization `ON` or `OFF` during workload replay. When synchronization is `ON`, the `COMMIT` order observed during the original workload capture will be preserved during replay. Every action that is replayed will be executed `ONLY` `AFTER` all of it's dependent `COMMIT`s (all `COMMIT`s that were issued before the given action in the original workload capture) have finished execution. `DEFAULT` is `TRUE` which preserves commit order.
`connect_time_scale`	Scales the time elapsed between the instant the workload capture was started and session connects with the given value. The input is interpreted as a % value. Can potentially be used to increase or decrease the number of concurrent users during the workload replay. `DEFAULT` `VALUE` is 100. See Application of the connect_time_scale Parameter.
`think_time_scale`	Scales the time elapsed between two successive user calls from the same session. The input is interpreted as a % value. Can potentially be used to increase or decrease the number of concurrent users during the workload replay. `DEFAULT` `VALUE` is 100. See Application of the think_time_scale Parameter.
`think_time_auto_correct`	Auto corrects the think time between calls appropriately when user calls takes longer time to complete during replay than how long the same user call took to complete during the original capture. `DEFAULT` is `TRUE` which is to reduce think time if replay goes slower than capture. See Application of the think_time_auto_correct Parameter

Usage Notes

Prerequisites:
- The database has been initialized for replay using the INITIALIZE_REPLAY Procedure.
- Any capture time connection strings that require remapping have been already done using the REMAP_CONNECTION Procedure.
One or more external replay clients (WRC) can be started once the PREPARE_REPLAY procedure has been executed.

Examples

Application of the connect_time_scale Parameter

If the following was observed during the original workload capture:

12:00 : Capture was started
12:10 : First session connect  (10m after)
12:30 : Second session connect (30m after)
12:42 : Third session connect  (42m after)

If the connect_time_scale is 50, then the session connects will happen as follows:

12:00 : Replay was started with 50% connect time scale
12:05 : First session connect  ( 5m after)
12:15 : Second session connect (15m after)
12:21 : Third session connect  (21m after)

If the connect_time_scale is 200, then the session connects will happen as follows:

12:00 : Replay was started with 200% connect time scale
12:20 : First session connect  (20m after)
13:00 : Second session connect (60m after)
13:24 : Third session connect  (84m after)

Application of the think_time_scale Parameter

If the following was observed during the original workload capture:

12:00 : User SCOTT connects
12:10 : First user call issued (10m after completion of prevcall)
12:14 : First user call completes in 4mins
12:30 : Second user call issued (16m after completion of prevcall)
12:40 : Second user call completes in 10m
12:42 : Third user call issued ( 2m after completion of prevcall)
12:50 : Third user call completes in 8m

If the think_time_scale is 50 during the workload replay, then the user calls will look something like below:

12:00 : User SCOTT connects
12:05 : First user call issued 5 mins (50% of 10m) after the completion of 
        previous call
12:10 : First user call completes in 5m (takes a minute longer)
12:18 : Second user call issued 8 mins (50% of 16m) after the completion of prev 
        call
12:25 : Second user call completes in 7m (takes 3 minutes less)
12:26 : Third user call issued 1 min  (50% of 2m) after the completion of prev 
        call
12:35 : Third user call completes in 9m (takes a minute longer)

Application of the think_time_auto_correct Parameter

If the following was observed during the original workload capture:

12:00 : User SCOTT connects
12:10 : First user call issued (10m after completion of prevcall)
12:14 : First user call completes in 4m
12:30 : Second user call issued (16m after completion of prevcall)
12:40 : Second user call completes in 10m
12:42 : Third user call issued ( 2m after completion of prevcall)
12:50 : Third user call completes in 8m

If the think_time_scale is 100 and the think_time_auto_correct is TRUE during the workload replay, then the user calls will look something like below:

12:00 : User SCOTT connects
12:10 : First user call issued 10 mins after the completion of prev call
12:15 : First user call completes in 5m (takes 1 minute longer)
12:30 : Second user call issued 15 mins (16m minus the extra time of 1m the prev 
        call took) after the completion of prev call
12:44 : Second user call completes in 14m (takes 4 minutes longer)
12:44 : Third user call issued immediately (2m minus the extra time of 4m the prev 
        call took) after the completion of prev call
12:52 : Third user call completes in 8m

PROCESS_CAPTURE Procedure

This procedure processes the workload capture found in capture_dir in place.

Syntax

DBMS_WORKLOAD_REPLAY.PROCESS_CAPTURE (
   capture_dir            IN   VARCHAR2);

Parameters

Table 145-10 PROCESS_CAPTURE Procedure Parameters

Parameter	Description
`catpure_dir`	Name of the workload capture directory object (case sensitive). The directory object must point to a valid OS directory that has the appropriate permissions. New files will be added to this directory. (Mandatory)

Usage Notes

This subprogram analyzes the workload capture found in the capture_dir and creates new workload replay specific metadata files that are required to replay the given workload capture. It only creates new files and does not modify any files that were originally created during the workload capture. Therefore, this procedure can be run multiple times on the same capture directory, such as when the procedure encounters unexpected errors or is cancelled by the user.
Once this procedure runs successfully, the capture_dir can be used as input to the INITIALIZE_REPLAY Procedure in order to replay the captured workload present in capture_dir.
Before a workload capture can be replayed in a particular database version, the capture needs to be "processed" using this PROCESS_CAPTURE procedure in the same database version. Once created, a processed workload capture can be used to replay the captured workload multiple times in the same database version.

For example, suppose workload "foo" was captured in rec_dir in Oracle database version 10.2.0.5. In order to replay the workload "foo" in version 11.1.0.1 the workload needs to be processed in version 11.1.0.1. The following procedure needs to be executed in a 11.1.0.1 database in order to process the capture directory rec_dir:
```
DBMS_WORKLOAD_REPLAY.PROCESS_CAPTURE('rec_dir');
```
Now, rec_dir contains a valid 11.1.0.1 processed workload capture that can be used to replay the workload "foo" in 11.1.0.1 databases as many number of times as required.

REMAP_CONNECTION Procedure

This procedure remaps the captured connection to a new one so that the user sessions can connect to the database in a desired way during workload replay.

Syntax

DBMS_WORKLOAD_REPLAY.REMAP_CONNECTION (
   connection_id         IN  NUMBER,
   replay_connection     IN  VARCHAR2);

Parameters

Table 145-11 REMAP_CONNECTION Procedure Parameters

Parameter	Description
`connection_id`	ID of the connection to be remapped.Corresponds to `DBA_WORKLOAD_CONNECTION_MAP`.`CONN_ID`
`replay_connection`	New connection string to be used during replay

Usage Notes

By default, all instances of replay_connection will be equal to NULL. When replay_connection is NULL (default), replay sessions will connect to the default host as determined by the replay client's runtime environment. Consequently, if no capture time connect strings are remapped, then all the replay sessions will simply connect to the default host to replay the workload.
A valid replay_connection should specify a connect identifier or a service point. Please refer to the Oracle Database Net Services Reference for ways to specify connect identifiers (such as net service names, database service names, and net service aliases) and naming methods that can be used to resolve a connect identifier to a connect descriptor.
An error is returned if no row matches the given connection_id.
Use the DBA_WORKLOAD_CONNECTION_MAP view to review all the connection strings that will be used by the subsequent workload replay, and also to examine connection string remappings used for previous workload replays.

REPORT Function

This function generates a report on the stipulated workload replay.

Syntax

DBMS_WORKLOAD_REPLAY.REPORT (
   replay_id          IN NUMBER,
   format             IN VARCHAR2 )
  RETURN CLOB;

Parameters

Table 145-12 REPORT Function Parameters

Parameter	Description
`replay_id`	Specifies the ID of the workload replay whose report is requested. (Mandatory)
`format`	Specifies the report format. Valid values are `XML`, `HTML`, or `TEXT`. (Mandatory)

Return Values

The report body in the desired format returned as a CLOB

Table 145-13 Constants Used by Report Function

Constant	Type	Value	Description
`TYPE_HTML`	`VARCHAR2`(4)	'HTML'	Generates the HTML version of the report
`TYPE_TEXT`	`VARCHAR2`(4)	'TEXT'	Use this as input to the `format` argument to generate the text version of the report.
`TYPE_XML`	`VARCHAR2`(3)	'XML'	Generates the XML version of the report

START_REPLAY Procedure

This procedure starts the workload replay. All the external replay clients (WRC) that are currently connected to the replay database will automatically be notified and those replay clients (WRC) will begin issuing the captured workload.

Syntax

DBMS_WORKLOAD_REPLAY.START_REPLAY;

Usage Notes

Prerequisites:
- The call to the PREPARE_REPLAY Procedure was already issued.
- Enough number of external replay clients (WRC) that can faithfully replay the captured workload have already been started. The status of such external replay clients can be monitored using V$WORKLOAD_REPLAY_CLIENTS.
Use the WRC's CALIBRATE mode to determine the number of replay clients that might be required to faithfully replay the captured workload. For example:
```
$ wrc mode=calibrate replaydir=.
```