11. Managing Archive 

11.1. Overview 

The Performance Co-Pilot includes many facilities for creating and replaying archives that capture performance information.

For all PCP monitoring tools, metrics values may come from a real-time feed (i.e. from pmcd on some host), or from an archive.

Users have complete control of what metrics are collected, how often and in which logs. These decisions can be changed dynamically.

11.2. Primary Logger 

The primary instance of the PCP archive logger (pmlogger) may be started on a collector system each time pmcd is started. To turn it on, as root do the following:
```
# chkconfig pmlogger on
# $PCP_RC_DIR/pcp start
```
The specification for hosts to log and pmlogger options is given in the $PCP_PMLOGGERCONTROL_PATH file and (optionally) files in the $PCP_PMLOGGERCONTROL_PATH.d directory.
This has a default entry for the local host, which specifies the metrics to be logged, and the frequency of logging - by default, using the file $PCP_VAR_DIR/config/pmlogger/config.default.

11.3. Other Logger Instances 

Additional instances of pmlogger may be started at any time, running on either a collector system or a monitor system.
In all cases, each pmlogger instance will create an archive for metrics from a single collector system.
The initial specification of what to log is given in a configuration file; the syntax is fully described in the pmlogger (1) man page.

11.4. Creating and Replaying PCP Archives 

Some configuration files are supplied, which may be found in the directory $PCP_VAR_DIR/config/pmlogger.
To create an archive and subsequent playback. Open a command shell and enter:
```
$ source /etc/pcp.conf
$ cd /tmp
$ rm -f myarchive.*
```
To start pmlogger with localhost as the default host from which metrics will be fetched, a logging duration of 30 seconds, a logging interval of 1 second, a configuration from the $PCP_VAR_DIR/config/pmlogger/config.mpvis file, and myarchive as the base name of the output archive:
```
$ $PCP_BINADM_DIR/pmlogger -T 30sec -t 1sec \ -c $PCP_VAR_DIR/config/pmlogger/config.mpvis myarchive
```
Once the archive has been created, the directory listing of myarchive.* shows that the archive created by pmlogger is composed of 3 files:
```
$ ls myarchive.*
```
mpvis is used for playbacks and all of the PCP monitoring tools accept the command line arguments -a archivename to replay from an archive:
```
$ mpvis -a myarchive
```
When mpvis starts up, in the PCP Archive Time Control dialog
- Single click on the Play button will start replaying values from the archive at the same speed at which they were recorded.
- Double click on thr play button will replay the values in a Fast Forward mode until it reaches the end of the archive.
- Select the Options->Show Bounds option to see the bounds of the archive.
Another way to look at the bounds of the archive is by using pmdumplog:
$ pmdumplog -L myarchive

11.5. Archive Folios 

To create an archive folio, open a command shell and enter:

$ source /etc/pcp.conf
$ cd /tmp
$ tar xzf $PCP_DEMOS_DIR/tutorials/pmie.tar.gz
$ tar xzf $PCP_DEMOS_DIR/tutorials/cpuperf.tar.gz
$ $PCP_BINADM_DIR/mkaf pmie/babylon.perdisk.0 \cpuperf/babylon.percpu.0 > myfolio

mkaf creates a folio called myfolio which includes the archives babylon.percpu and babylon.perdisk. Note that the archives are not changed in any way, and a new archive is not created.

pmafm tool may now be used to perform different operations on the folio myfolio, such as listing the folio contents, or using other tools to open the archives contained in the folio. If pmafm is given a folio name but no arguments, it will run in interactive mode.
$ pmafm myfolio list $ pmafm myfolio pmdumplog -l

For more information on folios refer to the mkaf(1) and pmafm(1) man pages.

11.6. Controlling pmlogger 

The pmlc utility may be used to interrogate any pmlogger instance running either locally or remotely. Use pmlc to

Add or delete metrics or metric instances to be logged

Change the logging frequency for selected metrics

The line-oriented command interface to pmlc(1) is fully described in the man page.

11.7. Management of PCP Archives 

PCP includes a suite of scripts and tools to automate the collection and management of archives.

Briefly, these facilities include:

daily log rotation (pmlogger_daily(1))
archive merging (pmlogextract(1))
automatic restarting of failed pmlogger instances (pmlogger_check(1))
creation of snapshots from archives (pmsnap(1))
maintenance of archive folios for active archives (mkaf(1) and pmafm(1))