DA-LOG files are log files used in connection with user spaces (see section “Logging”). These log files can be output using the SEDI70 utility (see the “Database Operation” manual).
Contents of DA-LOG files
In DA-LOG files, the SESAM/SQL DBH logs all changes to user spaces. Changes to user spaces occur as a result of SQL statements that change data and as a result of CALL DML statements.
In addition, SESAM/SQL uses DA-LOG files to document the creation of copies of the whole database or the catalog space and copies of user spaces. The creation of a copy of the database or catalog space automatically causes a change of DA-LOG file. The SESAM backup copies serve as resumption points when applying logged modifications during the repair of the database or the user spaces (see section “Recovering the database, catalog space and user spaces”).
Storage medium, primary and secondary assignments
SESAM/SQL creates the first DA-LOG file when the first change is made to a user space. The file is created on the storage medium (disk) and the primary assignment is made in accordance with the information in the first DA-LOG media record in the media table (the secondary assignment is always 0). SESAM/SQL creates subsequent DA-LOG files in accordance with the information given in the media table.
The following default values apply for primary and secondary assignment of the DA-LOG files: 768 (primary assignment) and 0 (secondary assignment).
BS2000 file name
DA-LOG files have the following name in BS2000:
user_id.catalog.version.D.nnnn
user_id | BS2000 user ID |
Opening the CAT-LOG file
If, when opening the DA-LOG file, at open time the storage media defined via CREATE MEDIA DESCRIPTION or ALTER MEDIA DESCRIPTION for the DA-LOG file are full or cannot be accessed, then CC occurs. After this CC, only read access to the database is possible. The CC changes the entry in the SQL database catalog from ACCESS=WRITE to ACCESS=READ.
To ensure that the file can be opened correctly, the user must create memory space on the relevant medium or make the medium accessible. If this not possible, issue a CREATE FILE command with the name of the DA-LOG file (name from the error message in the SYSLST file). The user must then use the SESADM administration program to reset the entry in the SQL database catalog to WRITE.
Switchover to a different DA-LOG file
SESAM/SQL switches to a different DA-LOG file in the following situations:
When a new SESAM backup copy of the whole database or the catalog space is created. The DA-LOG file is given the version number of the new SESAM backup copy of the catalog space and the serial number 0001, e.g. catalog.000017.D.0001.
The space in the DA-LOG file is exhausted.
An error occurs in the BS2000 DMS.
A user space has been repaired
If the storage medium in use is a magnetic tape cartridge, the DA-LOG file is also switched when the DBH starts up or restarts.
In the latter four cases, the new DA-LOG file retains the same version number as its predecessor and the serial number is incremented, e.g. catalog.000017.D.0002.
When the serial number nnnn of the DA-LOG file has reached the value 9999 and SESAM/SQL switches the DA-LOG file, the new DA-LOG file is given the version number incremented by one and the serial number 0001, e.g. catalog.000018.D.0001. In addition, a new CAT-LOG file with the version number incremented by one and the serial number 0001 is created, e.g. z.B. catalog.000018.C.0001
In addition, the CHANGE-DALOG administration statement can be used to switch the DA-LOG files to the specified database or databases (see the “Database Operation” manual). In this case, the version number also remains unchanged and the serial number is incremented by 1.