The HA for Sybase ASE fault monitor detects the following types of errors:
DBMS errors that occur during a probe of the database by the server fault monitor
Alerts that Sybase ASE logs in the Sybase ASE log file
Timeouts that result from a failure to receive a response within the time that is set by the Probe_timeout extension property
To define custom behavior for these types of errors, create a custom action file.
A custom action file is a plain text file. The file contains one or more entries that define the custom behavior of the HA for Sybase ASE fault monitor. Each entry defines the custom behavior for a single DBMS error, a single timeout error, or several logged alerts. A maximum of 1024 entries is allowed in a custom action file.
An entry in a custom action file consists of a sequence of keyword-value pairs that are separated by semicolons. Each entry is enclosed in braces.
The format of an entry in a custom action file is as follows:
{ [ERROR_TYPE=DBMS_ERROR|SCAN_LOG|TIMEOUT_ERROR;] ERROR=error-spec; [ACTION=SWITCH|RESTART|STOP|NONE;] [CONNECTION_STATE=co|di|on|*;] [NEW_STATE=co|di|on|*;] [MESSAGE="message-string"] }
White space might be used between separated keyword-value pairs and between entries to format the file.
The meaning and permitted values of the keywords in a custom action file are as follows:
Indicates the type of the error that the server fault monitor has detected. The following values are permitted for this keyword:
Specifies that the error is a DBMS error.
Specifies that the error is an alert that is logged in the alert log file.
Specifies that the error is a timeout.
The ERROR_TYPE keyword is optional. If you omit this keyword, the error is assumed to be a DBMS error.
Identifies the error. The data type and the meaning of error-spec are determined by the value of the ERROR_TYPE keyword as shown in the following table.
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You must specify the ERROR keyword. If you omit this keyword, the entry in the custom action file is ignored.
Specifies the action that the server fault monitor is to perform in response to the error. The following values are permitted for this keyword:
Specifies that the server fault monitor ignores the error.
Specifies that the server fault monitor is stopped.
Specifies that the server fault monitor stops and restarts the entity that is specified by the value of the Restart_type extension property of the SUNW.sybase resource.
Specifies that the server fault monitor switches over the database server resource group to another node or zone.
The ACTION keyword is optional. If you omit this keyword, the server fault monitor ignores the error.
Specifies the required state of the connection between the database and the server fault monitor when the error is detected. The entry applies only if the connection is in the required state when the error is detected. The following values are permitted for this keyword:
Specifies that the entry always applies, regardless of the state of the connection.
Specifies that the entry applies only if the server fault monitor is attempting to connect to the database.
Specifies that the entry applies only if the server fault monitor is online. The server fault monitor is online if it is connected to the database.
Specifies that the entry applies only if the server fault monitor is disconnecting from the database.
The CONNECTION_STATE keyword is optional. If you omit this keyword, the entry always applies, regardless of the state of the connection.
Specifies the state of the connection between the database and the server fault monitor that the server fault monitor must attain after the error is detected. The following values are permitted for this keyword:
Specifies that the state of the connection must remain unchanged.
Specifies that the server fault monitor must disconnect from the database and reconnect immediately to the database.
Specifies that the server fault monitor must disconnect from the database. The server fault monitor reconnects when it next probes the database.
The NEW_STATE keyword is optional. If you omit this keyword, the state of the database connection remains unchanged after the error is detected.
Specifies an additional message that is printed to the resource's log file when this error is detected. The message must be enclosed in double quotes. This message is additional to the standard message that is defined for the error.
The MESSAGE keyword is optional. If you omit this keyword, no additional message is printed to the resource's log file when this error is detected.
The action that the server fault monitor performs in response to each DBMS error is preset as listed in Figure 2, Table 2, Preset Actions for DBMS Errors. To determine whether you need to change the response to a DBMS error, consider the effect of DBMS errors on your database to determine if the preset actions are appropriate. For examples, see the subsections that follow.
To change the response to a DBMS error, create an entry in a custom action file in which the keywords are set as follows:
ERROR_TYPE is set to DBMS_ERROR.
ERROR is set to the error number of the DBMS error.
ACTION is set to the action that you require.
If an error that the server fault monitor ignores affects more than one session, action by the server fault monitor might be required to prevent a loss of service.
For example, see the following error message:
Illegal attempt to change contents of buffer: %S_BUF.
No action is preset for Sybase error 835, Illegal attempt to change contents of buffer: %S_BUF. However, this Sybase error indicates that the when a client process completes, Adaptive Server performs some cleanup tasks such as closing the buffers and releasing the resources taken up by the buffers. If the client process terminates abnormally, however (for example if the process is killed during execution), Adaptive Server might be unable to carry out the appropriate cleanup, buffers are left open, and Error 835 is raised. If this error affects only a single session, ignoring the error might be appropriate. However, if this error affects more than one session, consider specifying that the server fault monitor restart the database.
The following example shows an entry in a custom action file for changing the response to a DBMS error to restart.
Example 1 Changing the Response to a DBMS Error to Restart{ ERROR_TYPE=DBMS_ERROR; ERROR=835; ACTION=restart; CONNECTION_STATE=*; NEW_STATE=*; MESSAGE="Illegal attempt to change contents of buffer: %S_BUF."; }
This example shows an entry in a custom action file that overrides the preset action for DBMS error 835. This entry specifies the following behavior:
In response to DBMS error 835, the server fault monitor performs a restart.
This entry applies regardless of the state of the connection between the database and the server fault monitor when the error is detected.
The state of the connection between the database and the server fault monitor must remain unchanged after the error is detected.
The following message is printed to the resource's log file when this error is detected:
"Illegal attempt to change contents of buffer: %S_BUF."
If the effects of an error to which the server fault monitor responds are minor, ignoring the error might be less disruptive than responding to the error.
For example, see the following error message:
Unable to find buffer 0x%lx holding logical page %ld in sdes 0x%lx kept buffer pool for object '%.*s'.
The preset action for Sybase ASE error 804, Unable to find buffer 0x%lx holding logical page %ld in sdes 0x%lx kept buffer pool for object '%.*s'. is restart. This error occurs when Adaptive Server cannot find the pointer to a buffer header in a session descriptor. This error can be transient. In this situation, consider specifying that the server fault monitor ignore the error.
The following example shows an entry in a custom action file for ignoring a DBMS error.
Example 2 Ignoring a DBMS Error{ ERROR_TYPE=DBMS_ERROR; ERROR=804; ACTION=none; CONNECTION_STATE=*; NEW_STATE=*; MESSAGE="Unable to find buffer 0x%lx holding logical page %ld in sdes 0x%lx kept buffer pool for object '%.*s'."; }
This example shows an entry in a custom action file that overrides the preset action for DBMS error 804. This entry specifies the following behavior:
The server fault monitor ignores DBMS error 804.
This entry applies regardless of the state of the connection between the database and the server fault monitor when the error is detected.
The state of the connection between the database and the server fault monitor must remain unchanged after the error is detected.
No additional message is printed to the resource's log file when this error is detected.
The Sybase ASE software logs alerts in a file that is identified by the Adaptive_Server_Log_ File extension property. The server fault monitor scans this file and performs actions in response to alerts for which an action is defined.
Logged alerts for which an action is preset are listed in Figure 3, Table 3, Preset Actions for Sybase ASE Alerts. Change the response to logged alerts to change the preset action, or to define new alerts to which the server fault monitor responds.
To change the response to logged alerts, create an entry in a custom action file in which the keywords are set as follows:
ERROR_TYPE is set to SCAN_LOG.
ERROR is set to a quoted regular expression that identifies a string in an error message that Sybase ASE has logged to the Sybase ASE log file.
ACTION is set to the action that you require.
The server fault monitor processes the entries in a custom action file in the order in which the entries occur. Only the first entry that matches a logged alert is processed. Later entries that match are ignored. If you are using regular expressions to specify actions for several logged alerts, ensure that more specific entries occur before more general entries. Specific entries that occur after general entries might be ignored.
For example, a custom action file might define different actions for errors that are identified by the regular expressions Attempt to dirty non-log and Attempt to unhash buffer. To ensure that the entry that contains the regular expression Attempt to unhash buffer is not ignored, ensure that this entry occurs before the entry that contains the regular expression Attempt to.
The following example shows an entry in a custom action file for changing the response to a logged alert.
Example 3 Changing the Response to a Logged Alert{ ERROR_TYPE=SCAN_LOG; ERROR="Attempt to"; ACTION=RESTART; }
This example shows an entry in a custom action file that overrides the preset action for logged alerts about internal errors. This entry specifies the following behavior:
In response to logged alerts that contain the text Attempt to, the server fault monitor performs a restart.
This entry applies regardless of the state of the connection between the database and the server fault monitor when the error is detected.
The state of the connection between the database and the server fault monitor must remain unchanged after the error is detected.
No additional message is printed to the resource's log file when this error is detected.
By default, the server fault monitor restarts the database after the second consecutive timed-out probe. If the database is lightly loaded, two consecutive timed-out probes should be sufficient to indicate that the database is hanging. However, during periods of heavy load, a server fault monitor probe might time out even if the database is functioning correctly. To prevent the server fault monitor from restarting the database unnecessarily, increase the maximum number of consecutive timed-out probes.
![]() | Caution - Increasing the maximum number of consecutive timed-out probes increases the time that is required to detect that the database is hanging. |
To change the maximum number of consecutive timed-out probes allowed, create one entry in a custom action file for each consecutive timed-out probe that is allowed except the first timed-out probe.
For the last allowed timed-out probe, create an entry in which the keywords are set as follows:
ERROR_TYPE is set to TIMEOUT_ERROR.
ERROR is set to the maximum number of consecutive timed-out probes that are allowed.
ACTION is set to RESTART.
For each remaining consecutive timed-out probe except the first timed-out probe, create an entry in which the keywords are set as follows:
ERROR_TYPE is set to TIMEOUT_ERROR.
ERROR is set to the sequence number of the timed-out probe. For example, for the second consecutive timed-out probe, set this keyword to 2. For the third consecutive timed-out probe, set this keyword to 3.
ACTION is set to NONE.
The following example shows the entries in a custom action file for increasing the maximum number of consecutive timed-out probes to five.
Example 4 Changing the Maximum Number of Consecutive Timed-Out Probes{ ERROR_TYPE=TIMEOUT; ERROR=2; ACTION=NONE; CONNECTION_STATE=*; NEW_STATE=*; MESSAGE="Timeout #2 has occurred."; } { ERROR_TYPE=TIMEOUT; ERROR=3; ACTION=NONE; CONNECTION_STATE=*; NEW_STATE=*; MESSAGE="Timeout #3 has occurred."; } { ERROR_TYPE=TIMEOUT; ERROR=4; ACTION=NONE; CONNECTION_STATE=*; NEW_STATE=*; MESSAGE="Timeout #4 has occurred."; } { ERROR_TYPE=TIMEOUT; ERROR=5; ACTION=RESTART; CONNECTION_STATE=*; NEW_STATE=*; MESSAGE="Timeout #5 has occurred. Restarting."; }
This example shows the entries in a custom action file for increasing the maximum number of consecutive timed-out probes to five. These entries specify the following behavior:
The server fault monitor ignores the second consecutive timed-out probe through the fourth consecutive timed-out probe.
In response to the fifth consecutive timed-out probe, the server fault monitor performs a restart.
The entries apply regardless of the state of the connection between the database and the server fault monitor when the timeout occurs.
The state of the connection between the database and the server fault monitor must remain unchanged after the timeout occurs.
When the second consecutive timed-out probe through the fourth consecutive timed-out probe occurs, a message of the following form is printed to the resource's log file:
Timeout #number has occurred.
When the fifth consecutive timed-out probe occurs, the following message is printed to the resource's log file:
Timeout #5 has occurred. Restarting.