Magnetic Tape Deterioration and Data Recovery 3. TAPE DETERIORATION Apart from these manufacturing faults, tape deterioration can occur as a result of chemical reactions between the magnetic oxide, the binder, the lubricant, water vapour in the air, and particles of dirt from the air or from the tape head. Increases in temperature tends to act as a catalyst and speed up the deterioration process. The conditions under which tapes are stored are therefore a significant factor which affects deterioration. Manufacturers recommend that tapes should be stored at a temperature of about 20 degrees Centigrade and relative humidity of 50%. In the oil exploration industry tapes are often recorded and transported, and sometimes stored, in conditions which are far from this optimum. A few years ago one 3480 cartridge manufacturer experienced problems with lubricants escaping from the binder and damaging tape heads. The manufacturer blamed the problem on mis-handling of the cartridges by the shippers who reportedly left the cartridges outside and exposed to low temperatures. Manufacturers also recommend that tapes and cartridges should be cleaned and retensioned at least once per year, and preferably twice. Oil exploration tapes are usually stored for many years without being cleaned or exercised in any way. It is therefore perhaps not surprising that stiction problems do occur over a period of time. From our experience, there are three stages in the deterioration process: In stage one, there will be no obvious signs of deterioration, but when reading a tape the drive may detect some errors. Quite often the drive is able to correct the errors itself, and the user is unaware of any problems. Even as the errors become more severe and the drive is unable to correct them, the user will probably still be unaware that they exist - a few parity errors on a tape result in a few lost samples of data, but the user will almost certainly not realise this. In stage two, the deterioration process is greater and patches of tape will become "sticky". This results in the tape sticking to the recording head or the vacuum chamber as it is being read. Often there is an audible clicking sound as the tape is read, and the computer operator will find it necessary to clean the head more frequently. The number of parity errors and the amount of lost data will also increase, but it may still be insufficient for the explorationist to realise that there is a problem. The third stage of the deterioration process is the most severe. The binding agent has decomposed completely and the oxide is "flaking" off the tape. We have seen cases where large sections of oxide peel off the tape when it is read. Once this happens the data is lost irrecoverably, and the user certainly becomes aware of the problem. However, by then it is too late to do anything about it. How, therefore, is the explorationist able to determine whether his data archive has stiction problems before it becomes too late to recover the data. The answer is to perform a data audit. Table of Contents INTRODUCTION TAPE MANUFACTURING PROCESS TAPE DETERIORATION DATA AUDIT DATA RECOVERY SUMMARY See other technical papers.